Interior rearview mirror system including a forward facing video device

ABSTRACT

An interior rearview mirror system suitable for use in a vehicle includes a interior rearview mirror assembly adapted for attachment to an interior portion of the vehicle. The interior rearview mirror assembly includes a housing and a reflective element included within the housing. The mirror system further includes a video device (which includes an imaging sensor) and a control. The imaging sensor is positioned at the interior rearview mirror assembly and has a field of view forward and through the windshield. The imaging sensor is operable to at least sense precipitation at an interior and/or exterior surface of the windshield. The control receives a signal from the imaging sensor and is operable to control at least one of a headlamp of the vehicle, a windshield wiper of the vehicle, a defogging system of the vehicle and a movable window of the vehicle in response to the signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 09/346,352,filed Jul. 2, 1999 by Brent J. Bos et al. for RAIN SENSOR, now U.S. Pat.No. 6,313,454; and a continuation-in-part of U.S. patent applicationSer. No. 09/599,979, filed Jun. 22, 2000 by Kenneth Schofield et al. forVEHICLE RAIN SENSOR USING IMAGING SENSOR, now U.S. Pat. No. 6,320,176,which is a continuation of U.S. patent application Ser. No. 09/135,565,filed on Aug. 17, 1998 for VEHICLE HEADLAMP CONTROL USING IMAGINGSENSOR, now U.S. Pat. No. 6,097,023; and a continuation-in-part of U.S.patent application Ser. No. 09/776,625, filed Feb. 5, 2001 by KennethSchofield et al. for VEHICLE CAMERA DISPLAY SYSTEM, now U.S. Pat. No.6,611,202, which is a continuation of U.S. patent application Ser. No.09/313,139, filed May 17,1999 for REARVIEW VISION SYSTEM WITH INDICIA OFBACKUP TRAVEL, now U.S. Pat. No. 6,222,447, which is a continuation ofU.S. patent application Ser. No. 08/935,336, filed Sep. 22, 1997 forDISPLAY ENHANCEMENTS FOR VEHICLE VISION SYSTEM, now U.S. Pat. No.5,949,331; and a continuation-in-part of U.S. patent application Ser.No. 09/530,306, filed Apr. 27, 2000 by Kenneth Schofield et al. for RAINSENSOR WITH FOG DISCRIMINATION, now U.S. Pat No. 6,353,392, which is a371 national phase application of International PCT Application No.PCT/US98/23062, filed Oct. 30, 1998, which claims priority on U.S.provisional application, Ser. No. 60/064,335, filed Oct. 30, 1997, whichare all hereby incorporated in their entireties.

BACKGROUND OF THE INVENTION

This invention relates generally to vehicle moisture detection systemswhich detect precipitation on an outer surface of a vehicle window orwindshield and, more particularly, to a rain detector which is decoupledfrom the windshield and capable of detecting rain on an exterior surfaceof the window.

Several rain sensor systems have been proposed to date. Early systemswere typically closely coupled to the interior surface of thewindshield, such as by bonding to the glass surface or the like. Bypositioning the system immediately adjacent to the window, the rainsensor units sampled a relatively small area on the window. However,even the small sampling area may include many scratches, pits or othersurface irregularities on the window which may dominate the signalreceived by the rain sensor system, thereby leading to an erroneousdetection of rain on the window when little or no rain is actuallypresent. Furthermore, in order to achieve an adequate sampling area, agreater number of sampling channels is required, which results in anincrease of cost and bulk to the units. An additional concern withclosely coupled units is that they create difficulties in the vehicleassembly plants, since it is then necessary to handle two differentwindshield configurations in the factory, which increases inventorycosts. The close coupling also creates difficulties in the replacementof the windshield in the after market, since the rain sensor unit has tobe replaced along with the windshield if the windshield is damaged.

Other rain sensor devices have been proposed that are decoupled from thewindshield such that the sensors are spaced from the interior surface ofthe windshield, in order to avoid concerns with replacing the windshieldand other deficiencies present with the coupled systems. However, byspacing the rain sensor from the interior of the surface of the window,the rain sensor receives data from a larger sampling area on the window.This further increases the likelihood of significant errors in detectingrain droplets on the exterior of the windshield and discerning them fromscratches or other surface irregularities which may be present on thewindow. This is a greater concern when the rain sensor is operable on awindshield of a vehicle, since the exterior surface of a windshield istypically scratched and/or nicked in multiple places due to debrisimpacting the windshield as the vehicle is driven. Because the number ofsurface irregularities may be significantly greater than the amount ofprecipitation that may be present on the window, the rain sensor systemsmay result in erroneous detection of rain droplets when there is littleor no precipitation present on the window.

Other systems have recently been proposed which include an illuminationsource and an illumination sensor at an acute angle relative to oneanother, such that when the light from the illumination source isrefracted through the windshield and further reflected by water dropletson the exterior surface of the windshield, the light may be received bythe illumination sensor and processed to determine if precipitation ispresent on the exterior surface of the windshield. However, the additionof an illumination source further intensifies the appearance of thesurface irregularities which may be present on the window, since thelight reflects and scatters from the pits or scratches back toward thesensor, such that there is a greater likelihood that the surfaceirregularities will dominate the signal received by the illuminationsensor. This again may result in an erroneous detection of precipitationwhen there is little or no rain present on the window, since none ofthese systems account for any surface irregularities, such as scratchesor pits or the like, on the exterior and/or interior surfaces of thewindow.

SUMMARY OF THE INVENTION

The present invention is intended to provide a vehicular rain sensorwhich accurately detects rain on a vehicle window under a wide varietyof operating conditions, including when fog is present on the windshieldinterior, and provides the ability to separately detect the presence ofrain or fog on a window of a vehicle.

According to one aspect of the present invention, a rain sensor whichsenses precipitation at a vehicle window comprises an imaging arraysensor directed toward a vehicle window for detecting precipitation atthe window and a control which is responsive to the imaging array sensordetecting precipitation at the window. The control includes a filteringprocess. One function of the filtering process is to reduce the affecton the rain sensor of irregularities of the vehicle window, particularlysurface irregularities of the window.

According to another aspect of the invention, the control may include acomputer programmed with an edge detection algorithm, for detecting theedges of droplets of rain as they appear on the exterior surface of thewindshield. The control may be coupled to a windshield wiper such thatthe wipers are turned on when a predetermined threshold value ofprecipitation is detected on the window. An illumination source may alsobe implemented for illuminating the window when ambient light levels arelow. Preferably, the filtering process is operable to correct forsignals due to surface irregularities when the illumination source isactivated.

In one form, an optic may be included between the imaging array sensorand the windshield. The optic has a low f-ratio which provides a narrowdepth of field to the imaging array sensor, such that only the areaimmediately adjacent the windshield is in focus on the imaging arraysensor. The imaging array sensor and optic are oriented relative thewindshield to satisfy the Scheimpflug condition such that the opticfocuses an entire sampling area of the windshield onto thecorrespondingly angled imaging array sensor.

In another form, the vehicle rain sensor includes a polarizing filterthat is at least occasionally positioned in an optical path between theillumination source and the sensor to filter out polarized lightradiated from a fog particle on the inside of the window. The controlresponds to a signal from the sensor in order to indicate precipitationon an exterior surface of the window independent of moisture on aninterior surface of the window.

According to still yet another aspect of the present invention, avehicle rain sensor for detecting rain or fog on a vehicle windowcomprises at least one illumination source and at least one imagingsensor, defining at least one optic path therebetween. At least one ofthe optic paths is defined between at least one of the illuminationsources and the vehicle window, and between the vehicle window and atleast one of the imaging sensors. A polarizing filter is positionedalong at least one of the optic paths, and a control responds to anoutput of at least one of the illumination sensors in order to indicateprecipitation on an exterior surface of the window or fog on an interiorsurface of the window. The control includes a filtering process toaccount for irregularities such as surface irregularities of the vehiclewindow.

In one form, the control may communicate with the vehicle windshieldwipers and/or the rear window wipers when rain is detected on theexterior surface of the window and communicate with a blower within thevehicle to activate the blower when fog is detected on the interiorsurface of the window.

According to another aspect of the present invention, a vehicular sensoris adaptable for receiving a signal through a vehicle window. Thevehicular sensor comprises an imaging sensor directed at the window frominside the vehicle and a control. The control includes a filteringprocess to adjust an output of the imaging sensor in response to aplurality of signals in the output which are associated with surfaceirregularities on the vehicle window. The control then responds to anadjusted output of the imaging sensor.

The invention provides a new principle of detection which is decoupledfrom the windshield and may accurately detect the presence of rain onthe windshield and distinguish rain from other phenomena which could beconfused with rain, such as fog or surface irregularities associatedwith the window. The invention further optimizes rain sensing byfiltering the signal from the sensor to account for the surfaceirregularities on the window, thereby substantially precluding thelikelihood of a false rain detection by the sensor. The invention mayalso accurately provide for the separate detection of fog, therebyallowing further measures to be taken to improve driver visibility.

These and other objects, advantages, purposes and features of thisinvention will become apparent upon review of the followingspecification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a vehicle with a rain sensor with fogdiscrimination according to the present invention installed therein;

FIG. 2a is a sectional view taken along line II—II in FIG. 1;

FIG. 2b is the same view as FIG. 2a of an alternate embodiment of thepresent invention;

FIG. 3a-c are graphical illustrations of the geometric relationship ofthe elements of FIG. 1 in three dimensions;

FIG. 4 is a block diagram of an electronic control circuit;

FIG. 5a is an enlarged illustration of the optical features of raindroplets which are detected by an edge detection algorithm duringdaytime conditions;

FIG. 5b is the same view as FIG. 5a during nighttime conditions;

FIG. 6 is the same view as FIG. 4 of an alternate embodiment thereof;

FIG. 7 is a flow chart of an edge detection process performed by thecontrol circuit shown in FIG. 6;

FIGS. 8a-c are graphic representations of side elevations of analternate embodiment of a rain sensor with fog discrimination,illustrating operation thereof under different environmental conditions;

FIG. 9 is a perspective view of another alternate embodiment of a rainsensor with fog discrimination in the direction of the window interiorsurface;

FIG. 10a-c are side elevations of the embodiment illustration in FIG. 9illustrating operation thereof under different conditions;

FIG. 11 is the same view as FIG. 9 of another alternate embodimentthereof;

FIG. 12 is the same view as FIG. 9 of yet another alternate embodimentthereof;

FIG. 13 is the same view as FIG. 4 of another alternate embodimentthereof;

FIG. 14 is a simulated representation of rain droplets as sensed by asensor and illuminated by an illumination source associated with thepresent invention;

FIG. 15 is the rain droplet simulation of FIG. 14, with simulatedscratches and pits included on the window;

FIG. 16 is a simulated representation of the scratches and pits shown inFIG. 15;

FIG. 17 is a simulation of the scratches and pits of FIG. 16, after asmoothing algorithm has been performed on the data; and

FIG. 18 is a simulation similar to that of FIG. 15, after the smoothingalgorithm has been performed on the data collected.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now specifically to the drawings and the illustrativeembodiments depicted therein, a vehicle rain sensor system, generallyillustrated at 16, is positioned inside a vehicle 18 and directed towarda sampling area 48 of a window 19, which is illustrated as a windshieldof vehicle 18 also having a rear window 20 (FIG. 1). Vehicle 18 may beautomobile, a light truck, a van, a large truck, a sport utility vehicleor the like. Vehicle 18 further includes windshield wipers 22 for wipingprecipitation from an exterior surface 24 of window 19 and may alsoinclude a rear window wiper 26 for clearing rear window 20 ofprecipitation as it accumulates thereon. Rain sensor system 16 isconveniently incorporated in a rear view mirror assembly 30 attached toan interior surface 28 of front window, or to the roof above the frontwindow, by a mounting bracket 32, which is typically secured or bondedto interior surface 28 of window 19 by adhesive or the like (FIG. 2).Rain sensor 16 is preferably mounted within a pod 31 suspended frombracket 32 such that rain sensor system 16 is spaced from, or decoupledfrom, interior surface 28 of window 19. Such a pod 31 may of the typedisclosed in commonly assigned U.S. Pat. Nos. 5,576,687 and 5,708,410issued to Blank et al., the disclosures of which are hereby incorporatedherein by reference.

Rain sensor system 16 of the present invention includes an illuminationsensor or detector 36, which is preferably a multi-element,electro-optic, pixelated imaging array sensor, such as a CMOS imagingarray, CCD imaging array sensor or the like, a detailed description ofwhich is disclosed in commonly assigned U.S. Pat. No. 5,670,935, issuedto Schofield et al., patent application, Ser. No. 09/313,139, filed onMay 17, 1999, now U.S. Pat. No. 6,222,447, which is a continuation ofapplication Ser. Number 08/935,336, filed on Sep. 22, 1997, now U.S.Pat. No. 5,949,331, which is a continuation of the Schofield '935patent, the disclosures of which are hereby incorporated herein byreference.

Rain sensor 16 preferably includes a smoothing algorithm or filter 35which processes data sampled by illumination detector 36 in order toaccount for irregularities of the 7 window. Such irregularities arepredominately surface irregularities such as pits and/or scratches,which may be present in sampling area 48. Other irregularities mayinclude internal irregularities such as antenna and other insets in theglass, as well as lamination defects and the like. By mounting rainsensor system 16 in a rear view mirror bracket such that illuminationdetector 36 is directed toward the front of the vehicle, rain sensorsystem 16 may be adapted to also operate as a head lamp controller, asdisclosed in commonly assigned U.S. Pat. No. 5,796,094 issued toSchofield et al., and patent application, Ser. No. 09/135,565, filedAug. 17, 1998, now U.S. Pat. No. 6,097,023, which is a continuation ofthe Schofield '094 patent, the disclosures of which are herebyincorporated herein by reference. Furthermore, illumination detector 36may be adapted to function as a component of an active cruise controlsystem, whereby the detector functions to determine the speed at whichthe vehicle is travelling. Alternatively, if the rain sensor systemdisclosed herein were mounted such that illumination detector 36 werefacing rearward, toward rear window 20 of vehicle 18, illuminationdetector 36 may be adapted to function as a component of a vehicleback-up aid system. It is further envisioned that the smoothingalgorithm of the present invention may be applied to other vehicularvision or control systems, such as a wide angle image capture system ofthe type disclosed in commonly assigned United States Patentapplication, Ser. No. 09/199,907, filed on Nov. 25, 1998 by Brent J. Boset al., or a vision system of types disclosed in above referenced U.S.Pat No. 5,670,935 and in commonly assigned U.S. Pat. No. 5,550,677,issued to Schofield et al., the disclosures of which are herebyincorporated herein b reference

Illumination detector 36 is preferably a multi-element imaging arraymounted behind an optic lens 46 that is positioned between detector 36and windshield 19. Lens 46 is preferably designed to have a smallf-ratio in a range between approximately 0.8 and approximately 1.1, anda long focal length, preferably as long as possible while stillencompassing sampling area 48. This provides a narrow depth of field ofthe image, which results in detector 36 receiving a focused image ofonly the area immediately forward and rearward of window 19. Imagingarray detector 36, lens 46 and window 19 are all oriented relative oneanother according to the Scheimpflug relationship, which results inscenic information of sampling area 48 on window 19 being in focus ondetector 36, not withstanding the small f-ratio and long focal length ofthe optic. This relationship is commonly known in the field of opticalengineering and is illustrated in FIGS. 3a-c by a plane 49 passingthrough lens 46 and a plane, shown by dashed line 50, extending alongdetector 36, both of which intersect a plane defined by window 19 at aline 52 (FIG. 3c). This relationship applies three dimensionally, withplane 49 passing through lens 46 and plane 50 extending along detector36 intersecting the plane defined by window 19 at the same line 53 (FIG.3b). By orienting detector 36, lens 46 and window 19 in such a fashion,the entire angled surface of sampling area 48 on window 19 will bebrought into focus on the angled surface of detector 36.

As shown in FIG. 4, rain sensor 16 includes an electronic control 40having an A/D converter 37 which converts the analog informationcaptured by imaging array 36 into digital format for use in processingby filtering process 35 and an edge detection function 44. If the edgedetection function detects the presence of precipitation, such as raindroplets, a windshield wiper control 21 may activate the windshieldwipers 22 and/or modulate the wiper speed in proportion to the quantityof droplets detected. Although precipitation is disclosed hereinprimarily in reference to rain, it is intended to further include otherwater, such as snow melt, snow fall, road splash and other forms ofmoisture accumulation or deposition. Control 40 further includes adetection control function 42 which coordinates operation of the variouscomponents of control 40 so that individual capture frames of array 36are grabbed and processed. Preferably, the functions of control 40 areintegrated in a programmed computer or micro-computer, but may beindividually provided as discreet analog or digital components. If array36 includes interface circuitry capable of producing digital signals,the need for A/D converter 37 may be obviated. By the terms controland/or computer as used herein, it is envisioned that the presentinvention may include a micro-computer with an embedded controlapplication, a custom digital logic circuit, a digital signal processorcircuit or the like, which may be adaptable to be positioned within orin the vicinity of a rear view mirror housing.

Although edge detection function 44 detects the edges of rain dropletspresent on the window 19, other marks on window 19 associated withvarious irregularities, such as pits, scratches and/or defects of window19, or accessories on or within window 19, may also be detected by edgedetection function 44. Typically, the edges of raindrops at window 19may be less than ten millimeters across and more typically, less thanfive millimeters across their diameters, although many raindrops may belarger or smaller. However, most pits, scratches and/or defects ofwindow 19 are typically less than two millimeters in size. Althoughthese marks are typically smaller than the rain droplets, edge detectionfunction 44 may not be able to discern the droplets from the othermarks. Because the exterior surface 24 window 19 may become highlyscratched or pitted within a short period of time, the irregularities asdetected by edge detection function 44 may dominate over the number ofprecipitation droplets present at exterior surface 24, thereby resultingin an erroneous determination that the number of rain droplets detectedis above the predetermined threshold value. Therefore, control 40includes a digital filter or smoothing algorithm 35 in order to accountfor the surface irregularities on window 19 and thus reduce orsubstantially preclude the likelihood of an erroneous determination ofrain on window 19 when there is little or no precipitation thereon.

Smoothing algorithm 35 is preferably a local filter which smoothes thedata received by the pixilated imaging array 36 by changing the value ofan individual pixel based on information received from neighboringpixels. This process is reiterated for each individual pixel withinsampling area 48. The neighboring pixels may be immediately adjacent toor surrounding the individual pixel or may be within a predeterminedrange of pixels remote from the individual pixel. The selection of thesize and shape of a group or window or sub-array of pixels may varybased on the particular application of the rain sensor. Many suchsmoothing algorithms are known in the art of computer graphics and thelike, such as those used for removing random electronic noise fromremote sensing images. Preferably, smoothing algorithm 35 of control 40is a Median filter, Sigma filter or Nagao-Matsuyama filter, or somemodification of one or more of these filters such that smoothingalgorithm 35 is optimized for the particular sensor application.However, many other digital filtering processes are known and areavailable and a skilled artisan would select an appropriate or optimalalgorithm for the particular application of the present invention.

Because the irregularities, pits and/or scratches of a window aretypically very small, smoothing algorithm 35 may filter out or adjustdata associated with these small detected items, without significantlychanging the data values associated with the relatively large raindroplets and/or fog particles which may also be present on window 19.Smoothing algorithm 35 is preferably a local filter in that it modifiesa value of each individual pixel based on information received fromother pixels surrounding or neighboring the individual pixel to beadjusted. For example, a Median filter may utilize a 3×3 or 5×5 group orwindow of pixels and sets, or adjusts, the center pixel value inresponse to a calculated average of the values of the other pixelswithin the corresponding window. This averaging and resetting of pixelsis performed for each individual pixel of the imaging array sensor. Thisfiltering process thus removes or adjusts individual pixel valuesassociated with small pits or scratches, without removing orsignificantly changing pixel values associated with the largercontiguous edges of precipitation present on the window. This ispossible because within each small window, the pixel values associatedwith the smaller pits and scratches will not dominate the window or theother pixel values associated with a “clean” area of window 19. Thepixel values associated with the pits or scratches are therefore reducedor filtered out by the smoothing algorithm. The larger, contiguous edgesof the rain droplets, on the other hand, would not be significantlyaltered because these edges span more than one or two pixels, such thatan average window would contain several pixels associated with the edgesof the droplet.

The size and shape of the sampling window associated with this filteringprocess may be modified according to the particular application. If theirregularities making up the “bad” image portions of the array are onlyone to two pixels in size, then a small 3×3 pixel window shouldsubstantially preclude erroneous determinations by edge detectionfunction 44. On the other hand, if the pits and/or scratches are larger,then a larger window may be preferred. However, it is most preferable toimplement as small a window as possible in order to minimize the effecton the pixel values associated with rain droplet edges and thus theeffect on the number of actual rain droplet edges detected by edgedetection function 44.

Another known filter useful with the present invention is the Sigmafilter, which functions similarly to the Median filter discussed above.However, the Sigma filter averages the values of only those pixelswithin the window that are within a certain threshold limit of thecenter pixel value. Typically, this threshold limit is determined byplus or minus _(2σ) from the center value, where _(σ) is an assumed orestimated standard deviation of the irregularities or “bad” pixel valuesassociated with the sampling area 48 on window 19. The center pixelvalue for each window is then set to be the calculated average of thepixels that are within the pre-determined threshold for thecorresponding window. This process is reiterated for each pixel withinthe sampling area 48 on window 19.

Another known filter useful with the present invention is theNagao-Matsuyama filter, which rotates a group or window of pixels abouteach particular pixel in sampling area 48 in order to determine the mosthomogenous neighborhood area around each pixel. At each point ofrotation, both the mean and the variance of the pixel values within thewindow are calculated. A window of lowest variance may then bedetermined by comparing the values at each point of rotation. The valueof the target pixel, or the individual pixel around which the associatedwindow is rotated, is then adjusted or reset to the mean value of thepixels within the lowest variance window. This process is reiterated foreach pixel within sampling area 48. This filtering process may beoptimized for a particular application by changing the shape and/or thesize of the rotating window in order to better reject a particular typeof bad pixels which may be expected in the particular application, whilestill preserving the edges associated with actual rain droplets onwindow 19.

After smoothing algorithm 35 has been performed on data received bysensor 36, edge detection function, shown generally at 44 in FIG. 4,analyzes the signal from illumination detector 36 and determines thenumber of precipitation droplets present on exterior surface 24 bydetecting the edge of each droplet and further determining if the numberof edges detected is above a predetermined threshold value. Edgedetection function 44 allows imaging array detector 36 to interrogatemany complex patterns on a surface of window 19, instead of integratingthem together and thereby diluting the impact of the effects. The edgedetection function isolates and identifies the individual phenomenonthat become present on exterior surface 24 of window 19, which allowsthe system to separate out the multiple effects of the phenomena, ratherthan integrating them together. Such an edge detection algorithm iscommercially available and is marketed by MathWorks as a MATLAB imageprocessing toolbox EDGE routine. Alternately, an edgedetection/thresholding algorithm may be used that uses the Roberts,Prewitt, or Sobel approximation to the derivative, which are generallyknown in the art. While these algorithms are available and have beenused to test and evaluate the present invention, it is important to notethat many edge detection algorithms are commercially available and askilled artisan would select the appropriate algorithm for eachapplication of the present invention. For example, an edge detectionalgorithm may analyze precipitation droplets in a linear manner, wherethe algorithm enhances the edges as received by the imaging arraydetector and counts the contiguous droplets present within the samplingarea. Alternatively, an edge detection algorithm may enhance and thenfurther analyze the droplets according to the number of droplets and thesize of their contiguous edges or other characteristics. Therefore, byimplementing an imaging array sensor for illumination detector 36 andfurther utilizing a filtering process 35 and an edge detection algorithm44, the effects of fog or fogging on the interior surface 28 of window19, and of other interferences, may be significantly reduced as the rainsensor actually receives and analyzes the contiguous droplet edgespresent within an image of sampling area 48 on window 19, rather thanmerely receiving a pulse of light reflecting or emitting from an objecton window 19.

Control 40 may be used to control windshield wipers 22 on front window19 and may further be used to control rear window wipers 26 on rearwindow 20 of the vehicle 18. Control 40 may activate rear wiper 26 atthe same or different rate as front wipers 22. For example, for every Nwipes of front wiper 32, control 40 may generate a command for rearwiper 26 to wipe one time. N is preferably some number greater than 1 sothat rear wiper 26 does not wipe as often as front wiper 22. Control 40may further vary the rate of rear wiper 26 based on the wipe rate offront wipers 22, which may also be varied depending on the level ofprecipitation detected on exterior surface 24 of window 19. Furthermore,the edge detection function may provide various thresholds at whichcontrol 40 activates the wipers at different speeds. For example, whenthe size and/or number of contiguous edges is low, the wipers may beactivated for only a single wipe across the windshield or rear window,whereas when the size and/or number of the contiguous edges increases, acontinuous low speed wipe may be provided or even a continuous highspeed wipe as the size and/or number of contiguous edges detectedfurther increases.

In an alternate embodiment of a vehicle rain sensor system 16′,illustrated in FIG. 2b, an illumination source 38 is also positionedwithin pod 31 to provide illumination to sampling area 48 of window 19.This allows illumination detector 36 to operate in low ambient lightconditions by illuminating raindrops present on the window. Whenprecipitation or fog is present at window 19, illumination emitting fromillumination source 38 is reflected and refracted by the window and theprecipitation droplets such that illumination is received byillumination detector 36. However, when neither fog nor rain is presentat window 19, illumination detector 36 does not directly receive anysubstantial amount of light emitting from illumination source 38, aslight emitting from illumination source 38 reflects downward frominterior surface 28 of window 19 or refracts through window 19, ratherthan reflecting toward illumination detector 36.

While illumination source 38 enhances the ability of the rain sensor todetect precipitation on window 19, this also intensifies images receivedby illumination detector 36 which are associated with irregularities ofwindow 19. When the rain sensor is operable in ambient light conditions,such irregularities are typically barely visible due to their small sizeand thus are not as readily detectable by edge detection algorithm 44.However, when the rain sensor is operable with illumination source 38,the illumination from illumination source 38 reflects and scatters fromthese irregularities back toward illumination detector 36, such that thesignals received by detector 36 are more difficult to discern betweenthose associated with a rain droplet or with a scratch on window 19.Accordingly, the rain sensor most preferably includes a smoothingalgorithm 35 which is operable when illumination source 38 is alsoactivated. As discussed above, however, smoothing algorithm 35 may alsobe operable when no illumination source is activated. In order tofurther optimize rain detection in both lighting conditions, smoothingalgorithm 35 may function in one manner when illumination source 38 isactivated while operating in another manner when illumination source 38is deactivated. This may be accomplished by changing the size or shapeof the window or by changing the threshold criteria within eachsmoothing algorithm.

Illumination source 38 may be a standard photodiode, infrared energyemitter or the like, and is preferably operable in a pulse mode. Mostpreferably, rain sensor 16′ is coordinated such that illumination source38 is pulsed to illuminate the area on the window while illuminationdetector is simultaneously exposed to the area. Illumination detector 36may be either mechanically or electronically shuttered open at theprecise moment that illumination source 38 is pulsed or activated. Thisresults in a more efficient system by avoiding the operation ofillumination source 38 except for those moments when illumination sensor36 is actually receiving an image. This also allows a high peakillumination, as provided by illumination source 38, to be more readilyextracted from the background ambient lighting. Because an imaging arraysensor may process either visible light or invisible, infrared ranges,illumination source 38 of the present invention may provide illuminationat a preferred wavelength which is between the visible ranges andinfrared ranges. Therefore, illumination source 38 is preferably a LEDwhich emits energy pulses having a wavelength near that of infraredlight, such that the beam emitted is substantially invisible to thehuman eye, yet may still pass through the infrared filtercharacteristics within certain vehicle's windows. Most preferably, theenergy emitted by illumination source 38 has a wavelength within therange of approximately 820 to 880 nanometers, which may be transmittedthrough the filtering characteristics of a window and processed byimaging array sensor 36.

A control 40′ useful with rain sensor system 16′ includes an ambientlight logic function 54 to determine the level of ambient light presenton window 19 and switch rain sensor system 16′ between a passive mode,where illumination source 38 is not used, when light present on window19 is provided by ambient light, and an active mode, where illuminationsource 38 is activated by an illumination source control 55, andpatterns are illuminated on windshield 19 by illumination source 38 andreceived by imaging array 36 (FIG. 6). Preferably, illumination sourcecontrol 55 activates illumination source 38 when the illumination leveldetected by ambient light logic function 54 is below a threshold valueof approximately 250 lux. More preferably, the active mode is triggeredwhen the illumination level detected is below approximately 150 lux, andmost preferably, when the illumination level detected is belowapproximately 100 lux. Alternatively, illumination source control 55 mayactivate illumination source 38 in response to a signal from a head lampcontroller to activate the headlights of the vehicle, or in response tothe headlights being otherwise activated. Control 40′ may activatesmoothing algorithm 35 only when illumination source 38 is activated ormay activate smoothing algorithm 35 each time an image is received byillumination detector 36. Control 40′ may also activate a differentversion of smoothing algorithm 35 in response to activation ordeactivation of illumination source 38.

Most preferably, ambient light logic function 54 is responsive to theoutput of A/D converter 37 to determine ambient conditions from a lightlevel sensed by imaging array sensor 36. More particularly, presentambient light conditions may be determined by summing the signal valuesreceived by each pixel within the imaging array sensor. When the sum ofthe values is above a predetermined threshold value, rain sensor system16′ operates in its passive mode and edge detection algorithm 44analyzes the image as discussed above, while if the sum is below thepredetermined threshold value, rain sensor system 16′ instead operatesin its active mode where ambient logic function 54 causes illuminationsource control 55 to activate illumination source 38. When in the activemode, illumination source 38 may be turned on in a pulse mode, so thatillumination detector 36 receives several images to extract the signalfrom any noise that may be present. Preferably, smoothing algorithm 35is activated when rain sensor 16′ is operating in the active mode inorder to minimize the effect of scratches and the like which may bepresent on or within window 19. Once the noise has been removed from thesignal, and erroneous values have been accounted for by algorithm 35,control function 42 determines if the level of precipitation, if any, isabove a predetermined threshold value. If rain is detected, wipercontrol 21 activates front wipers 22, and may also operate rear wiper26, as necessary.

Typical raindrops, as received by an imaging array sensor, arerepresented at 57 in FIGS. 5a and 5 b. FIG. 5a shows an image of raindrops 57 on windshield 19 during daytime light conditions, when thesystem 16′ may be in a passive mode. FIG. 5b shows images of typicalraindrops 57 on window 19 when the system 16′ is in an active mode atnight lighting conditions. This is shown on a “clean” window which hasno scratches or pits on its surfaces. When precipitation droplets 57,such as from rain, dew or the like, are present on exterior surface 24of window 19 in area 48 during the daytime, the light received byillumination detector 36 includes dark rings 56, which correspond to theedges of the precipitation droplets 57 present on window 19, as bestshown in FIG. 5a. Conversely, when rain sensor 16′ is in an active modeat nighttime, the edges of precipitation droplets 57 form images oflight rings 58 on a dark background 59, as shown in FIG. 5b.

Although edge detection function 44 detects and calculates the number ofedges 56 and 58 of precipitation droplets 57, window 19 will typicallyinclude many other marks associated with scratches, pits, defects or thelike and detected by imaging array sensor 36. Referring now to FIGS. 14to 18, a simulation is shown of a typical sampling area as detected bysensor 36 when illumination source 38 is activated. As discussed above,rain droplets 57 appear as light rings on a dark background. The raindroplets 57 are simulated in FIGS. 14-18 as dark rings or dots on alight or white background. However, as shown in FIG. 15, a typicalsampling area 48 provides images associated with the precipitationdroplets 57 along with a high number of other signals, typicallyassociated with irregularities of window 19, such as pits or scratcheson the window surface, which are represented by the smaller dots 61.Without any smoothing algorithm or filter process, edge detectionfunction 44 would count each signal received as a rain droplet, therebyresulting in a substantial error in the number of droplets on window 19determined by edge detection function 44. For example, the simulatedsampling area of FIG. 15 results in a count of approximately 10,000edges or droplets, when an accurate count of only the rain droplet edges(FIG. 14) should have resulted in a count of only approximately 2500edges.

The effects of smoothing algorithm 35 are best shown in reference toFIGS. 16 to 18. When no rain is present on window 19, imaging arraysensor 36 detects surface irregularities as simulated in FIG. 16. Asmentioned above, this figure is a simulation of the scratches and pitswhich may occur to a vehicle window 19 over time, due to debris and thelike impacting the exterior surface 24 of window 19 as the vehicle isdriven. The number of irregularities thus vary across the surface of thewindow and may further vary over time as additional pits, scratches andthe like may later occur. By activating smoothing algorithm 35, many ofthe irregularities may be filtered and/or averaged out of the datareceived by sensor 36, such that edge detection function 44 analyzes andcounts a substantially fewer number of pits as edges of rain drops. Thesimulation of FIG. 16 is shown again in FIG. 17 after smoothingalgorithm 35 has been performed, resulting in a substantially “cleaner”sampling area 48 on window 19. In testing smoothing algorithm 35 on thissimulation, the number of pits detected was reduced from approximately9200 (FIG. 16) to less than 500 (FIG. 17), after smoothing algorithm 35was performed.

Referring now to FIG. 18, data associated with rain droplets andirregularities of sampling area 48 and received by sensor 36 is shownafter smoothing algorithm 35 has been applied. The pixel values havebeen adjusted such that the number of pits 61 detected has beensubstantially reduced by smoothing algorithm 35 as compared to theinitial unfiltered sample shown in FIG. 15, while the edges of thedroplets 57 have not been greatly affected. Testing has shown that theerror associated with the unfiltered sample may be reduced fromapproximately 300% (FIG. 15) to less than only 2% (FIG. 18) byimplementing digital filter or smoothing algorithm 35. As seen in FIG.18, rain droplet edges can then be accurately detected and counted byedge detection function 44, since the number of edges representing raindroplets dominates over the remaining images representing surfaceirregularities on window 19.

The edge detection function 44 in control 40′ functions to detect andanalyze the droplets 57 and further determines a density of raindrops onarea 48 of window 19. In either day or night conditions, the same edgedetection algorithm may be applied to detect the edges and count thenumber of rain drops present on window 19, and compare that amount to apredetermined threshold value. Most preferably, smoothing algorithm 35is operable when rain sensor 16′ is in its active mode, since this modesubstantially increases the error associated with irregularities ofwindow 19. However, smoothing algorithm 35 may also be operable when therain sensor is in its passive mode. Once the number of droplets 57 thatare detected is above a predetermined threshold value, control 40′operates to activate windshield wipers 22, including modulating thewiper speed as a function of the sensed raindrop density. Preferably,the threshold value may be changed as the level of ambient lightchanges, since the driver of a vehicle becomes more sensitive toraindrops on the windshield as ambient conditions get darker. Therefore,the edge detection algorithm may have a lower threshold value duringnight-time conditions than during daytime conditions. The thresholdvalue may change as rain sensor system 16′ is switched between itsactive and passive modes.

Referring now to FIG. 7, a flow chart of a control process 200 of rainsensor system 16′ begins at 205 by first grabbing an image 210 receivedby imaging array sensor and resetting the number of edge counts by edgedetection function to zero 220. The sum of the light values sensed bythe pixel in imaging array sensor is then determined and compared to athreshold value 230. If it is determined at 230 that the sum is greaterthan the threshold value, then the edge preserving smoothing algorithmmay be activated at 235 and then the edge detection function isactivated 240. Alternately, the smoothing algorithm may not be activatedat 235 and may only be activated in situations where it is determined at230 that the sum of the light values is less than the threshold value,as discussed below. The edges detected are then analyzed at 245 todetermine if the number and/or size of the edges detected is greaterthan a threshold value. If it is determined at 245 that the numberand/or size of the edges detected is greater than a threshold value,control process 200 functions to activate the wipers at 250. If theedges detected are less than the threshold value a “wiper off” signal issent at 260. After the control sends the appropriate signal, the systemreturns 270 to its initial settings and resumes the sampling process205.

If it is determined at 230 that the sum of the light values sensed byimaging array sensor are less than the threshold values, ambient senselogic function 54 activates or pulses an illumination source at 280.When the illumination source is pulsed, three more images aresimultaneously taken at 290 by imaging array sensor, while threeadditional images are grabbed between the pulses or when theillumination source is otherwise off at 300. The control process thensubtracts the data collected during the “off” frames from the datacollected during the “on” frames at 310 to remove any noise from thesignals. Once the noise has been removed, the edge preserving smoothingalgorithm 35 is activated at 315 to remove or average a majority of anyerroneous pixel data from the sampling signals. Following this filteringprocess, the edge detection function 44 is activated at 320 and thenumber and/or size of the edges detected are compared to a thresholdvalue 330. If it is determined at 330 that the number and/or size of theedges are greater than the threshold value, the illumination source isdeactivated 340 and a signal is communicated to activate the wipers 250at an appropriate speed. On the other hand, if the number of edgesdetected is less than the threshold value, the illumination source isdeactivated at 350 and a “wiper off” signal is communicated at 260. Onceeither signal is communicated to the wipers, the system 16′ againreturns 270 to its initial settings and resumes the sampling process205.

In an alternate embodiment, a rain sensor system 120 further includes apolarizing filter 62. This may allow rain sensor system 120 to discernbetween rain 57 and fog or fogging 66 on window 19, such that controlfunction 42 may activate either wipers 22 or blower 60 when necessary,as discussed below. Fog or fogging as used herein refers to condensationor moisture forming on interior surface 28 of window 19, and may includefogging on exterior surface 24 of window 19, such as in situations wherean air conditioner is directed toward window 19 and moisture condenseson exterior surface 24 as the window is cooled. Polarizing filter 62 ispositioned along an optic path 64 between illumination source 38 andillumination detector 36, and may be located between illumination source38 and window 19 or between illumination detector 36 and window 19. Byincluding a polarizing filter 62 according to the present invention,illumination detector 36 may be an inexpensive single elementphoto-sensor or the like, while still enabling rain sensor system 120 todetect and discriminate between fog and rain at window 19, therebyachieving optimal performance of the system at a potentially lower costthan a multi-element imaging array sensor.

Referring now to FIGS. 8a, 8 b and 8 c, illumination source 38,illumination detector 36 and polarizing filter 62 are shown unattachedto any base or bracket for clarity only, and are preferably mountedwithin a rear view mirror bracket or the like, as discussed above.Polarizing filter 62 is shown positioned between window 19 andillumination detector 36 and substantially reduces light that isoppositely polarized from a pass axis 67 within polarizing filter 62.When there is neither precipitation droplets present on exterior surface24 of window 19 nor fog particles present on interior surface 28 ofwindow 19, as illustrated in FIG. 8a, illumination detector 36 does notdirectly receive any substantial amount of light emitting fromillumination source 38. This is due to the angle of window 19 relativeillumination source 38 and detector 36, as light emitting from source 38reflects downward from interior surface 28 of window 19 or refractsthrough window 19. However, as precipitation droplets become present onwindow 19 or fog particles 66 accumulate on interior surface 28 ofwindow 19, light that radiates from illumination source 38 is directedtoward illumination detector 36 as it either scatters and reflects dueto rain droplets 57 on exterior surface 24 or is reemitted by a particleof fog 66 on interior surface 28 of window 19.

As illustrated in FIG. 8b, polarizing filter 62 substantially reduceslight radiating from fog particle 66 that is received by illuminationsensor 36. This is possible due to the fact that for most media, lightis a transverse electromagnetic field, such that a non-polarized lightray, represented by line 68, has electromagnetic fields, generallyrepresented by arrows 70, in all directions perpendicular to thedirection that the light wave is traveling. Therefore, in order forlight to propagate in any direction, the electromagnetic fieldcoincident with the light ray must oscillate perpendicular to thedirection of travel. When incident unpolarized light 68 is absorbed by asmall enough particle, such as a particle of fog 66 or the like, theelectrons of the particle vibrate in the directions of electromagneticfields 70 present in the incident unpolarized light 68. The intensity ofthe light radiating from a small particle when illuminated by polarizedlight varies according to the equation:${{I(\theta)} = \frac{\rho_{o}^{2}\omega^{4}\sin^{2}\theta}{32\quad \pi^{2}c^{3}ɛ_{o}r^{2}}};{{{where}\quad \omega} = \frac{2\pi \quad c}{\lambda}};$

where_(ρ) ₀ is the dipole moment, _(Ω) is the angular frequency oflight, _(λ) is the wavelength of light, _(c) is the speed of light, _(ε)₀ is the permittivity of free space, _(r) is the distance that the lightis from the dipole, and _(θ) is the angle of the radiated light relativeto the direction of oscillation of the electrons in the particle. Fornon-polarized light striking a small particle, the overall intensity ofthe light radiated from the particle is a linear superposition of theintensities from each electromagnetic field oscillating within theincident light. As the light is radiated in a direction perpendicular tothe incident ray of light, _(θ) is approximately zero relative to theelectrons oscillating along one of the electromagnetic fields, whichresults in a substantially zero intensity of light in that directionthat is supported by that particular electromagnetic field. On the otherhand, _(θ) is simultaneously approximately 90 degrees relative to thedirection of oscillation of electrons oscillating along another of theelectromagnetic fields, which results in the light supported by thesecond electromagnetic field being at its greatest intensity. Therefore,the superposition of these intensities results in a light ray 72re-emitting from a fog particle 66 that is substantially linearlypolarized light when the emitted light propagates at approximately 90degrees relative to the direction of the incident light, as the otherdirections of oscillation either were not present in the incidentunpolarized light 68 or otherwise cannot support propagation of thelight. However, as the size of the particle increases, such as to thesize of a rain droplet, the polarization effect goes away. Therefore,while light re-emitting from a fog particle is substantially linearlypolarized, light reflecting and scattering from a precipitation dropletis primarily non-polarized.

Preferably, illumination source 38 and illumination detector 36 areoriented relative one another at approximately an 80 to 100 degree angleat interior surface 28 of window 19. Most preferably, this angle isapproximately 90 degrees. Polarizing filter 62 may be placed betweenwindow 19 and illumination detector 36 such that its pass axis 67 isperpendicular to an electromagnetic field present in the linearpolarized light 72 emitting from the fog particle 66. As shown in FIG.8b, for example, with illumination detector 36 and source 38 beingoriented substantially horizontally, the polarized light 72 emittingfrom fog particle 66 toward illumination detector 36 is substantiallyvertically polarized. By orienting the pass axis 67 of polarizing filter62 substantially horizontally, there will be substantial filtering ofthe polarized light ray 72 before it is received by illuminationdetector 36. Therefore, when fog particles 66 are present on interiorsurface 28 of window 19, illumination detector 36 receives a very weaksignal, similar to the signal received when there is neither rain norfog present on the window, thereby substantially reducing anypossibility of illumination detector 36 receiving a false signal of raindroplets when there is merely fog particles 66 present on interiorsurface 28 of window 19.

As shown in FIG. 8c, when a precipitation droplet 57 is present onexterior surface 24 of window 19, incident unpolarized light 68 refractsthrough window 19 and reflects within the water droplets 57, resultingin a scattering of light back toward interior surface 28 of window 19.The light is reflected and scattered in many directions such that asubstantial amount of light may be received by illumination detector 36,thereby generating a signal that there is rain present on exteriorsurface 24 of window 19. The scattered light remains unpolarized andthus passes through polarizing filter 62, as polarizing filter 62 merelypolarizes the light, thereby allowing light that has its electromagneticfields (shown as a horizontal line 73) substantially similar to the passaxis 67 of polarizing filter 62 to pass therethrough. Therefore,illumination detector 36 still receives a stronger signal when there areprecipitation particles 57 on exterior surface 24 of window 19 than whenthere is either fog particles 66 present on interior surface 28 ofwindow 19 or when there is neither fog nor rain present on window 19.After illumination detector 36 receives the polarized light ray aspolarized by polarizing filter 62, control function 42 again functionsto analyze the signal received and determine whether wipers 22 and 26should be activated, as discussed above.

Alternately, polarizing filter 62 may be movably positioned in opticpath 64, to allow illumination detector 36 to receive a signalalternating from polarized to non-polarized light by occasionallypositioning polarizing filter 62 in optic path 64. This allows rainsensor system 120 to further discern between when fog is present, whenrain is present, when both rain and fog are present, and when neitherrain nor fog is present. The difference between the polarized andnon-polarized signals received by illumination detector 36 is greaterwhen fog is present on the window, compared to the difference betweenthe strong signals received when rain alone is present on window 19.When fog is detected by control function 42, the intensity of eachsignal is measured to further determine if rain is also present onexterior surface 24. Subsequently, control 40′ may further communicatewith blower 60 within vehicle 18 to operate blower 60 and eliminate thefog on the interior surface of window 19 when a threshold value of fogis detected, while also activating wipers 22 if necessary. When weaksignals are received both when the polarizer is present and when notpresent, neither rain nor fog is present on window 19.

In an alternate embodiment, as shown in FIGS. 9 and 10, a rain sensorsystem 130 further includes a second illumination detector 74 whichdefines a second optic path 76 between illumination source 38 and seconddetector 74 via window 19. A polarizing filter 62 may be positioned atany point along one or the other of the two optic paths 64 and 76. Asshown in FIG. 9, polarizing filter 62 may be positioned betweenillumination detector 74 and window 19. Because polarizing filter 62 ispositioned along optic path 76, illumination source 38 and secondillumination detector 74 are preferably oriented relative one another atapproximately an 80 to 100 degree angle at interior surface 28 of window19, and most preferably at approximately a 90 degree angle. Illuminationdetector 36 may then be positioned substantially adjacent detector 74,preferably with an angle A between detectors 36 and 74 being minimizedto be as close to zero degrees as possible, such that both detectorsreceive substantially the same light signal from window 19. When neitherfog nor rain is present on window 19, as shown in FIG. 10a, neitherfirst illumination detector 36 nor second illumination detector 74receives a strong signal directly from illumination source 38. However,when rain is present on window 19, polarizing filter 62 polarizes alight ray 78 from illumination source 38 along optic path 76, such thata polarized light ray 80, which is received by illumination detector 74,is linearly polarized in one direction only, such as in the horizontaldirection shown in FIG. 10c. A non-polarized light ray 82 issimultaneously received by first illumination detector 36. Therefore,when rain drops or other precipitation droplets are present on exteriorsurface 24 of window 19, both illumination detectors 36 and 74 willreceive a signal as the non-polarized light rays 78 and 82 arereflected, refracted and scattered by the droplets present on window 19,such that a substantial portion of the scattered light is directedtoward both illumination detectors 36 and 74. Because light ray 78 isnot polarized when it reaches polarizing filter 62, polarizing filter 62merely polarizes the light, which still allows polarized light ray 80 tobe received by illumination detector 74.

When fog particles 66 alone are present at interior surface 28 of window19, as shown in FIG. 10b, a polarized light ray 86 from fog particle 66is emitted only in directions perpendicular to an incident ray of light88 from illumination source 38. As discussed above, the orientation ofillumination detector 74 relative to illumination source 38 ispreferably at approximately a 90 degree angle along optic path 76, suchthat polarized light ray 86 is directed toward illumination detector 74.Therefore, polarizing filter 62, with its pass axis 67 oriented in adirection perpendicular to the electromagnetic field 92 in polarizedlight ray 86, functions to substantially filter out polarized light ray86 so that substantially no signal is received by illumination detector74 when fog is present on interior surface 28 of window 19. Conversely,illumination detector 36 simultaneously receives a non-filtered lightray 84 when fog is present on window 19. Light ray 84 may also besubstantially polarized if illumination detector 36 is also orientedrelative to illumination source 38 at approximately a 90 degree angle atwindow 19.

Because illumination detectors 36 and 74 receive different signals whenfog is present, when rain is present, when both rain and fog are presentand when neither rain nor fog is present on window 19, control function42 may analyze the signals received by both illumination detectors 36and 74 to determine if either fog is present on interior surface 28 orprecipitation is present on exterior surface 24 of window 19 or both fogand precipitation are present. If the signal received by illuminationdetector 36 is approximately equal to twice the signal received bysecond illumination detector 74, then no fog is present, asnon-polarized light passes through polarizing filter 62 and is receivedby illumination detector 74. Control function 42 then measures theintensity of the signals to determine if rain is present, as rainresults in a greater intensity in the signal received due to scatteringof light from rain droplet 57. On the other hand, if a signal isreceived by illumination detector 74, yet the signal received byillumination detector 36 is substantially greater than twice the signalreceived by second illumination detector 74, then control function 42may conclude that fog is present on interior surface 28 of window 19,and activate blower 60 to defog the interior surface 28 of window 19. Iffog is detected, control function 42 further measures and compares theintensities of the signals to determine if rain is also present onexterior surface 24. Illumination detectors 36 and 74 may either besingle element photo-sensors or multi-element imaging arrays, both ofwhich are capable of receiving the different signals reflecting oremitting from objects on window 19.

Another alternate embodiment of the present invention is shown in FIG.11, where a rain sensor system 140 includes two illumination sources 38and 94, one illumination detector 36 and a polarizing filter 62. In thisembodiment, polarizing filter 62 may be positioned between illuminationsource 94 and window 19, such that illumination detector 36 receiveslight from a polarized source 94 and an unpolarized source 38.Illumination sources 38 and 94 are cycled alternately such thatillumination detector 36 and control function 42 may determine whichillumination source 38 or 94 the signal is being received from. Theorientation of polarized source 94 and illumination detector 36 ispreferably within a range of approximately 80 to 100 degrees relativeone another, and most preferably approximately 90 degrees relative oneanother. This embodiment functions similar to those described above, inthat when there is neither rain nor fog present on window 19,illumination detector 36 receives substantially no signal from bothillumination sources 38 and 94. However, when small fog particles arepresent on interior surface 28 of window 19, a polarized beam or ray 96,having an electromagnetic field 95 in a single direction which issubstantially perpendicular to light ray 96, passes through linearpolarizer 62 and is absorbed and re-emitted by the particles. Accordingto the light intensity equation for I(_(θ)) discussed above, whenlinearly polarized light strikes a fog particle, the intensity of lightre-emitted will be approximately zero in a direction that is both alongthe direction of the electromagnetic field 95 present in the polarizedray of light and perpendicular to the incident ray of light, as theangle _(θ) will be zero in that direction. By positioning illuminationdetector 36 along a path in this direction, illumination detector 36receives substantially no signal from polarized illumination source 94when fog is present on the interior surface 28 of window 19, yet stillreceives a strong signal from unpolarized illumination source 38. On theother hand, if rain alone is present on window 19, illumination detector36 receives a strong signal from illumination source 38 andapproximately a one-half signal from illumination source 94.Furthermore, if both fog and rain are present on window 19, illuminationdetector 36 again receives a strong signal from illumination source 38,but receives a signal from illumination source 94 that is greater thanthe approximately zero intensity signal received when fog alone ispresent, but less than the approximately one-half signal received whenrain alone is present on window 19. Control function 42 compares thesignals received from each illumination source 38 and 94 to determine iffog, rain, both fog and rain or neither fog nor rain is present onwindow 19, and correspondingly activate or deactivate the appropriatedevice. Illumination detector 36 of rain sensor system 140 is preferablyan imaging array sensor, but may alternatively be a single elementphoto-sensor or the like.

Still yet another embodiment of the present invention is shown in FIG.12, where a rain sensor system 150 includes a single illumination source38 and two illumination detectors 36 and 102. A polarizing filter 62 ispositioned between illumination source 38 and window 19, such that alight ray 104 from illumination source 38 is polarized to become apolarized light ray 106 before reflecting or emitting from window 19.Both detectors 36 and 102 are preferably oriented within a range ofapproximately 80 to 100 degrees relative one another, as represented byan angle B in FIG. 12, and further oriented within a range ofapproximately 80 to 100 degrees relative polarized illumination source38. Most preferably, illumination detectors 36 and 102 and illuminationsource 38 are oriented at approximately 90 degrees relative one another.Polarizing filter 62 has little effect on rain sensor system 150 whenrain is present on window 19 or when neither rain nor fog is present onwindow 19. However, when fog particles 66 are present on interiorsurface 28 of window 19, polarized light ray 106 is absorbed by fogparticles 66 and is re-emitted with a minimal or substantially zerointensity in a direction parallel to the electromagnetic field that waspresent in polarized light ray 106. Therefore, by polarizing the lightin the horizontal direction, as shown in FIG. 12, light in a verticaldirection, or perpendicular to the pass axis 67 or polarizedelectromagnetic field, is emitted by the small particle of fog 66 with amuch greater intensity than the light propagating parallel to theelectromagnetic field. This results in second illumination detector 102receiving polarized light 108 re-emitted from a fog particle, whilefirst illumination detector 36 receives substantially no signal when fogis present on the interior surface of window 19. If the signal receivedby illumination detector 36 is approximately the same as the signalreceived by second illumination detector 102, then control function 42may conclude that no fog is present on interior surface 28 of window 19.The intensity of the signals are then analyzed and compared to determineif rain alone is present on window 19. However, if the signal receivedby second illumination detector 102 is substantially greater than thesignal received by illumination detector 36, then fog is present oninterior surface 28 of window 19, and control function 42 maysubsequently operate the blower to eliminate the fog and further comparethe intensities of the signals received to determine if rain is alsopresent on window 19.

Referring now to FIG. 13, an alternate embodiment of a rain sensorsystem 160 is diagrammed. Rain sensor system includes at least oneillumination source 38, at least one illumination sensor 36 and apolarizing filter (not shown). A control 40″ useful with rain sensorsystem 160 includes an ambient light logic function 54 to determine theintensity of ambient light and switch rain sensor system 160 betweenactive and passive modes, as discussed above. Most preferably, ambientlogic function 54 responds to the output of A/D converter 37 todetermine ambient conditions as sensed by at least one of the imagingarray sensors and further communicates with illumination source control55 if ambient light is below a threshold value. Illumination sourcecontrol 55 activates at least one of the illumination sources 38 so thatlight may be received by imaging array sensors 36. The polarizing filter62 is positioned along at least one optic path between the illuminationsources and the illumination sensors so as to filter or polarize lightbefore it is received by at least one of the sensors, similar to theembodiments discussed above. Preferably, smoothing algorithm 35 isactivated to average or smooth the sampled data to, for example, accountfor scratches and/or pits in window 19, as discussed above. Edgedetection function 44 then analyzes the signal or signals received bythe illumination sensor or sensors to determine if there is rain alone,fog alone, both rain and fog, or neither rain nor fog present on window19. If rain is detected, edge detection function 44 determines if theamount of rain is above a threshold value, while if fog is detected, thecontrol 40″ further analyzes the signals to determine if the level offog is above a threshold value. Accordingly, either wipers 22, blower 60or both are activated by control 40″, if necessary.

While several alternate embodiments have been depicted and describedabove, clearly the present invention may include other variations wherethere are one or two illumination sources and detectors, with at leastone polarizing filter positioned along an optic path defined by one ofthe illumination detectors and one of the illumination sources viawindow 19, without affecting the scope of the present invention.Polarizing filter 62 may be positioned between an illumination sourceand window 19 or between an illumination detector and window 19, and maybe oriented such that its pass axis 67 allows linearly polarized lightto pass therethrough in such a fashion as to allow the rain sensorsystem to discern between unpolarized light being scattered from raindrops 40 on exterior surface 24 of window 19 and linearly polarizedlight being emitted from a particle of 66 on interior surface 28 ofwindow 19. Although shown and described as detecting fogging at a frontwindshield of vehicle 18, the rain sensor of the present invention maydetect fogging at interior and/or exterior surfaces of other windows onvehicle 18, such as side or rear windows. The rain sensor may furthercontrol an appropriate blower to direct dryer air toward the window atwhich the fogging was detected in order to reduce the fogging on thatparticular window. Most preferably, in order to optimize the rain sensorsystem so as to best determine when fog or fogging is present atinterior surface 28 of window 19, at least one set of illuminationsources and sensors is preferably oriented such that the optical path tothe corresponding sensor or source is at approximately a 90 degree anglebetween the source and sensor at the interior surface 28 of window 19.This orientation best allows the system to determine when smallparticles of fog are present, while not inadvertently concluding thatfog is present when rain is actually present on exterior surface 24.

Although shown and described as being useful with a rain sensor,filtering process 35 may be useful with other vehicular systems whichinclude an imaging sensor which receives an image through a window orwindshield. For example, filtering process 35 may be useful withvehicular headlamp controls of the type disclosed in commonly assignedU.S. Pat. No. 5,796,094, vehicle back up aids of the type disclosed incommonly assigned co-pending patent application, Ser. No. 09/199,907,filed Nov. 25, 1998 by Bos et al., the disclosure of which is herebyincorporated herein by reference, or other vehicular vision systems.Filtering process 35 may then filter or smooth data associated withirregularities on the window or transparent panel through which thevision system is directed, while having a minimal affect on headlightand taillight or rearward scene data received by the particular imagingsensors.

The concepts of the present invention may be used in association withrain sensor interior mirror assemblies wherein a rain sensorfunctionality is provided in association with an interior rearviewmirror assembly. Such association includes utilizing an element of therearview mirror assembly (such as a plastic housing attached, forexample, to the mirror channel mount that conventionally attaches themirror assembly to a windshield button slug) to cover awindshield-contacting rain sensor. The rearview mirror assembly caninclude a display function (or multiple display functions).

These displays may perform a single display function or multiple displayfunctions such as providing indication of an additional vehiclefunction, such as a compass mirror display function, a temperaturedisplay functions, status of inflation of tires display function, apassenger air bag disable display function, an automatic rain sensoroperation display function, telephone dial information display function,highway status information display function, blind spot indicatordisplay function, or the like, such display may be an alpha-numericaldisplay or a multi-pixel display, and may be fixed or scrolling. Such anautomatic rain sensor operation display function may include a displayfunction related to a both a windshield-contacting and anon-windshield-contacting rain sensor, including, for example, where thecircuitry to control the rain sensor, electrochromic dimming of avariable reflectance electrochromic mirror, and any other mirror-mountedelectronic feature are commonly housed in or on a rearview mirrorassembly and wholly or partially share components on a common circuitboard. The blind spot detection display or the automatic rain sensoroperation display may alternate with other display functions by adisplay toggle which may be manually operated, time-shared,voice-actuated, or under the control of some other sensed function, suchas a change in direction of the vehicle or the like. Should a rainsensor control be associated with, incorporated in, or coupled to theinterior rearview mirror assembly, the rain sensor circuitry, inaddition to providing automatic or semi-automatic control over operationof the windshield wipers (on the front and/or rear windshield of thevehicle), can control the defogger function to defog condensed vapor onan inner cabin surface of a vehicle glazing (such as the inside surfaceof the front windshield, such as by operating a blower fan, heaterfunction, air conditioning function, or the like), or the rain sensorcontrol can close a sunroof or any other movable glazing should rainconditions be detected. As stated above, it may be advantageous for therain sensor control (or any other feature such as a head-lampcontroller, a remote keyless entry receiver, a cellular phone includingits microphone, a digital voice recorder, a video camera for a videophone, a taxi meter and/or taxi meter display, a vehicle statusindicator and the like) to share components and circuitry with theelectrochromic mirror function control circuitry and electrochromicmirror assembly itself. Also, a convenient way to mount anon-windshield-contracting rain sensor such as described herein is byattachment, such as by snap-on attachment, as a module to the mirrorchannel mount such as is described in U.S. Pat. No. 5,576,678 entitled“Mirror Support Bracket,” invented by R. Hook et al. and issued Nov. 19,1996, the disclosure of which is hereby incorporated by referenceherein. The mirror mount and/or windshield button may optionally bespecially adapted to accommodate a non-windshield-mounting rain sensormodule. Such mounting as a module is readily serviceable and attachableto a wide variety of interior mirror assemblies (both electrochromic andnon-electrochromic such as prismatic, manually adjusted mirrorassemblies), and can help ensure appropriate alignment of thenon-windshield-mounted variety of rain sensor to the vehicle windshieldinsofar that the module attached to the mirror mount remains fixedwhereas the mirror itself (which typically attaches to the mirrorchannel mount via a single or double ball joint) is movable so that thedriver can adjust its field of view. Also, should smoke from cigarettesand the like be a potential source of interference to the operation ofthe non-windshield-contacting rain sensor, then a mirror-attachedhousing can be used to shroud the rain sensor unit and shield it fromsmoke (and other debris). Optionally, such ability to detect presence ofcigarette smoke can be used to enforce a non-smoking ban in vehicles,such as is commonly requested by rental car fleet operators. Also, whena rain sensor (contacting or non-contacting) is used to activate thewiper on the rear window (rear backlight) of the vehicle, the sensor canbe conveniently packaged and mounted with the CHMSL (center high mountedstop light) stop light assembly commonly mounted on the rear windowglass or close to it. Mounting of the rain sensor with the CHMSLstoplight can be aesthetically appealing and allow sharing ofcomponents/wiring/circuitry.

The concepts of this present invention can be used with interiorrearview mirrors equipped with a variety of features such as a high/low(or daylight running beam/low) headlamp controller, a hands-free phoneattachment, a video camera for internal cabin surveillance and/or videotelephone function, seat occupancy detection, map reading lights,compass/temperature display, taxi meter display, fuel level and othervehicle status display, a trip computer, an intrusion detector and thelike. Again, such features can share components and circuitry with theelectrochromic mirror circuitry and assembly so that provision of theseextra features is economical.

Placement of a video camera either at, within, or on the interiorrearview mirror io assembly (including within or on a module attached toa mirror structure such as the mount that attaches to the windshieldbutton) has numerous advantages. For example, the mirror is centrallyand high mounted and the camera can be unobtrusively mounted.

Therefore, a rain sensor is disclosed herein that provides an accuratemethod of detecting rain on a vehicle window by actually capturing animage of an area on the window and further determining when the amountof precipitation present on the window reaches a predetermined thresholdvalue before activating the wiper system of the vehicle. The rain sensorpreferably includes a filtering or smoothing algorithm in order toaccount for scratches on the vehicle window, thereby substantiallyprecluding false rain detection due to scratches or pits which occur ona vehicle window surface over time. The rain sensor may further detectboth fogging and rain at the window, and is able to discriminatetherebetween. The rain sensor of the present invention is also decoupledfrom the window to avoid replacement concerns and the like that arepresent with many of the rain sensors in use today. Furthermore, therain sensor of the present invention provides optimal performance bydetecting both fog and rain on the window, while providing a system thatmay implement standard, low cost single element photo-sensors andphotodiodes or the like.

Changes and modifications in his specifically described embodiments canbe carried out without departing from the principles of the invention,which is intended to be limited only by the scope of the appendedclaims, as interpreted according to the principles of patent law.

The embodiments of the invention in which an exclusive property right orprivilege is claimed are defined as followed:
 1. An interior rearviewmirror system suitable for use in a vehicle, said interior rearviewmirror system comprising: an interior rearview mirror assembly adaptedfor attachment to an interior portion of the vehicle, said interiorrearview mirror assembly comprising a housing and a reflective elementincluded within said housing; and a video device, said video deviceincluding an imaging sensor, said imaging sensor being positioned atsaid interior rearview mirror assembly and having a field of viewforward and through the windshield, said imaging sensor being operableto at least sense precipitation at at least one of an exterior surfaceof the windshield and an interior surface of the windshield; and acontrol operable to receive a signal from said imaging sensor, saidcontrol being operable to control a headlamp of the vehicle and tocontrol at least one of a windshield wiper of the vehicle and adefogging system of the vehicle in response to said signal wherein saidimaging sensor is operable as a component of an active cruise controlsystem.
 2. The interior rearview mirror system of claim 1, wherein saidimaging sensor is operable to determine the speed at which the vehicleis traveling.
 3. An interior rearview mirror system suitable for use ina vehicle, said interior rearview mirror system comprising: an interiorrearview mirror assembly adapted for attachment to an interior portionof the vehicle, said interior rearview mirror assembly comprising ahousing and a reflective element included within said housing; and avideo device, said video device including an imaging sensor, saidimaging sensor being positioned at said interior rearview mirrorassembly and having a field of view forward and through the windshield,said imaging sensor being operable to at least sense precipitation at atleast one of an exterior surface of the windshield and an interiorsurface of the windshield; and a control operable to receive a signalfrom said imaging sensor, said control being operable to control aheadlamp of the vehicle and to control at least one of a windshieldwiper of the vehicle and a defogging system of the vehicle in responseto said signal, said imaging sensor being operable to sense waterdroplets at the exterior surface of the windshield and fog particles atthe interior surface of the windshield, said control being operable tocontrol a windshield wiper of the vehicle in response to the presence ofwater droplets at the exterior surface of the windshield and to controla defogging system of the vehicle in response to the presence of fogparticles at the interior surface of the windshield, wherein saidcontrol is operable to control a headlamp of the vehicle in response tothe presence of water droplets at the exterior surface of thewindshield.
 4. The interior rearview mirror system of claim 3, whereinsaid control is operable to control a headlamp of the vehicle inresponse to a level of light present at the windshield.
 5. The interiorrearview mirror system of claim 4, wherein said control is operable tocontrol a movable window of the vehicle in response to the presence ofwater droplets at the exterior surface of the windshield.
 6. An interiorrearview mirror system suitable for use in a vehicle, said interiorrearview mirror system comprising: an interior rearview mirror assemblyadapted for attachment to an interior portion of the vehicle, saidinterior rearview mirror assembly comprising a housing and a reflectiveelement included within said housing; and a video device, said videodevice including an imaging sensor, said imaging sensor being positionedat said interior rearview mirror assembly and having a field of viewforward and through the windshield, said imaging sensor being operableto at least sense precipitation at at least one of an exterior surfaceof the windshield and an interior surface of the windshield; and acontrol operable to receive a signal from said imaging sensor, saidcontrol being operable to control a headlamp of the vehicle and tocontrol at least one of a windshield wiper of the vehicle and adefogging system of the vehicle in response to said signal, said imaginesensor being operable to sense water droplets at the exterior surface ofthe windshield and fog particles at the interior surface of thewindshield, said control being operable to control a windshield wiper ofthe vehicle in response to the presence of water droplets at theexterior surface of the windshield and to control a defogging system ofthe vehicle in response to the presence of fog particles at the interiorsurface of the windshield, said control being operable to vary a rate ofwine of a windshield wiper of the vehicle wherein said control isoperable to vary the rate of wipe according to a density of waterdroplets on the exterior surface of the windshield.
 7. The interiorrearview mirror system of claim 6, wherein said control is operable tocontrol a movable window of the vehicle in response to said signal. 8.The interior rearview mirror system of claim 7, wherein said control isoperable to control a sunroof of the vehicle to close the sunroof inresponse to the presence of precipitation at the exterior surface of thewindshield.
 9. The interior rearview mirror system of claim 6, whereinsaid control comprises a micro-computer having at least one of anembedded control application, a custom digital logic circuit and adigital signal processor circuit.
 10. The interior rearview mirrorsystem of claim 9, wherein said imaging array comprises circuitrycapable of producing at least one digital signal.
 11. The interiorrearview mirror system of claim 10, wherein said control is operable todigitally process said at least one digital signal.
 12. The interiorrearview mirror system of claim 6, wherein said control is operable tocontrol a headlamp of the vehicle in response to a level of light sensedat the vehicle.
 13. The interior rearview mirror system of claim 12,wherein said imaging sensor is operable to sense a level of ambientlight present at the vehicle.
 14. The interior rearview mirror system ofclaim 13, wherein said control is operable to control a headlamp of thevehicle in response to said imaging sensor sensing low light conditions.15. The interior rearview mirror system of claim 6, wherein saidinterior rearview mirror assembly comprises an electrochromic interiorrem-view mirror assembly and said reflective element comprises anelectrochromic reflective element, said electrochromic interior rearviewmirror assembly comprising electrochromic control circuitry forcontrolling said electrochromic reflective element.
 16. The interiorrearview mirror system of claim 15, wherein said control shares at leastone component of said electrochromic control circuitry.
 17. The interiorrearview mirror system of claim 16, wherein said control shares said atleast one component on a common circuit board of said electrochromicinterior rearview mirror assembly.
 18. The interior rearview mirrorsystem of claim 6, wherein said control is operable to control at leastone other accessory of the vehicle.
 19. The interior rearview mirrorsystem of claim 6, including an illumination device for illuminating thefield of view of said imaging sensor.
 20. The interior rearview mirrorsystem of claim 19, wherein said illumination device provides infraredillumination.
 21. The interior rearview mirror system of claim 19,wherein said illumination device is at least occasionally activated. 22.The interior rearview mirror system of claim 21, wherein saidillumination device is pulsed on and off.
 23. The interior rearviewmirror system of claim 6, wherein said imaging sensor comprises animaging array sensor.
 24. The interior rearview mirror system of claim23, wherein said imaging array sensor comprises a pixelated imagingarray sensor.
 25. The interior rearview mirror system of claim 23,wherein said imaging array sensor comprises a CMOS sensor.
 26. Theinterior rearview mirror system of claim 6, wherein said video deviceincludes a lens disposed between said imaging sensor and the interiorsurface of the windshield.
 27. The interior rearview mirror system ofclaim 26, wherein said lens functions to establish a small depth offield.
 28. The interior rearview mirror system of claim 27, wherein saidlens focuses said imaging sensor on an area at or immediately adjacentto the windshield of the vehicle.
 29. An interior rearview mirror systemsuitable for use in a vehicle, said interior rearview mirror systemcomprising: an interior rearview mirror assembly adapted for attachmentto an interior portion of the vehicle, said interior rearview mirrorassembly comprising a housing and a reflective element included withinsaid housing; and a video device, said video device including an imagingsensor, said imaging sensor being positioned at said interior rearviewmirror assembly and having a field of view forward and through thewindshield, said magma sensor being operable to at least senseprecipitation at at least one of an exterior surface of the windshieldand an interior surface of the windshield; and a control operable toreceive a signal from said imaging sensor, said control being operableto control a headlamp of the vehicle and to control at least one of awindshield wiper of the vehicle and a defogging system of the vehicle inresponse to said signal, said imaging sensor being operable to sense fogparticles at the interior surface of the windshield, said control beingoperable to control a defogging system of the vehicle in response tosaid imaging sensor sensing fog particles at the interior surface of thewindshield wherein said control is operable to adjust a blower level ofthe defogging system of the vehicle in response to a density of the fogparticles sensed at the interior surface of the windshield.
 30. Theinterior rearview mirror of claim 29, wherein said F system imagingsensor is operable to sense water droplets at an exterior surface of thewindshield, said control being operable to control a windshield wiper ofthe vehicle in response to said imaging sensor sensing water droplets atthe exterior surface of the windshield.
 31. The interior rearview mirrorsystem of claim 30, wherein said control is operable to adjust a rate ofwipe of a windshield wiper of the vehicle.
 32. The interior rearviewmirror system of claim 31, wherein said control is operable to adjustthe rate of wipe in response to a quantity of the water droplets sensedat the exterior surface of the windshield.
 33. The interior rearviewmirror system of claim 31, wherein said control is operable to control arear window wiper of the vehicle.
 34. The interior rearview mirrorsystem of claim 33, wherein said control is operable to control a rearwindow wiper in response to said imaging sensor sensing water dropletsat the exterior surface of the windshield.
 35. An interior rearviewmirror system suitable for use in a vehicle, said interior rearviewmirror system comprising: an interior rearview mirror assembly adaptedfor attachment to an interior portion of the vehicle, said interiorrearview mirror assembly comprising a housing and a reflective elementincluded within said housing; and a video device, said video deviceincluding an imaging sensor, said imaging sensor being positioned atsaid interior rearview mirror assembly and having a field of viewforward and through the windshield, said imaging sensor being operableto at least sense precipitation at at least one of an exterior surfaceof the windshield and an interior surface of the windshield; and acontrol operable to receive a signal from said imaging sensor, saidcontrol being operable to control a headlamp of the vehicle and tocontrol at least one of a windshield wiper of the vehicle and adefogging system of the vehicle in response to said signal, said imagingsensor being operable to sense water droplets at an exterior surface ofthe windshield, said control being operable to control a windshieldwiper of the vehicle in response to said imaging sensor sensing waterdroplets at the exterior surface of the windshield, said control beingoperable to adjust a rate of wipe of a windshield wiper of the vehicleand said control being operable to control a rear window wiper of thevehicle, said control being operable to control the rear window wiper inresponse to said imaging sensor sensing water droplets at the exteriorsurface of the windshield, wherein said control causes a rear windowwiper to cycle for every N cycles of a windshield wiper, wherein N isgreater than one.
 36. The interior rearview mirror system of claim 35,wherein the value of N varies as a function of the speed of a windshieldwiper.
 37. An interior rearview mirror system suitable for use in avehicle, said interior rearview mirror system comprising: an interiorrearview mirror assembly adapted for attachment to an interior portionof the vehicle, said interior rearview mirror assembly comprising ahousing and a reflective element included within said housing; and avideo device, said video device including an imaging sensor, saidimaging sensor being positioned at said interior rearview mirrorassembly and having a field of view forward and through the windshield,said imaging sensor being operable to at least sense precipitation at atleast one of an exterior surface of the windshield and an interiorsurface of the windshield: a control operable to receive a signal fromsaid imaging sensor, said control being operable to control a headlampof the vehicle and to control at least one of a windshield wiper of thevehicle and a deforming system of the vehicle in response to saidsignal; and an illumination device for illuminating the field of view ofsaid imaging sensor, said illumination device being pulsed on and off,wherein said imaging sensor comprises a shutter for exposing saidimaging sensor to the field of view forwardly and through thewindshield.
 38. The interior rearview mirror system of claim 37, whereinduring low light conditions, said shutter is opened to expose saidimaging sensor to the windshield when said illumination device is pulsedon and closed to not expose said imaging sensor to the windshield whensaid illumination device is pulsed off.
 39. An interior rearview mirrorsystem suitable for use in a vehicle, said interior rearview mirrorsystem comprising: an interior rearview mirror assembly adapted forattachment to an interior portion of the vehicle, said interior rearviewmirror assembly comprising a housing and a reflective element includedwithin said housing; and a video device, said video device including animaging sensor, said imaging sensor being positioned at said interiorrearview mirror assembly and having a field of view forward and throughthe windshield, said imaging sensor being operable to at least senseprecipitation at at least one of an exterior surface of the windshieldand an interior surface of the windshield; a control operable to receivea signal from said imaging sensor, said control being operable tocontrol a headlamp of the vehicle and to control at least one of awindshield wiper of the vehicle and a defogging system of the vehicle inresponse to said signal; and an illumination device for illuminating thefield of view of said imagine sensor, said illumination device being atleast occasionally activated, wherein said illumination device isactivated during low light conditions.
 40. The interior rearview mirrorsystem of claim 39, wherein said imaging sensor is operable to sensewater droplets at the exterior surface of the windshield and fogparticles at the interior surface of the windshield.
 41. The interiorrearview mirror system of claim 40, wherein said control is operable tocontrol a windshield wiper of the vehicle in response to the presence ofwater droplets at the exterior surface of the windshield and to controla defogging system of the vehicle in response to the presence of fogparticles at the interior surface of the windshield.
 42. The interiorrearview mirror system of claim 41, wherein said control is operable tovary a rate of wipe of a windshield wiper of the vehicle.
 43. Theinterior rearview mirror system of claim 39, wherein said imaging sensoris operable to sense fog particles at the interior surface of thewindshield, said control being operable to control a defogging system ofthe vehicle in response to said imaging sensor sensing fog particles atthe interior surface of the windshield.
 44. An interior rearview mirrorsystem suitable for use in a vehicle, said interior rearview mirrorsystem comprising: an interior rearview mirror assembly adapted forattachment to an interior portion of the vehicle, said interior rearviewmirror assembly comprising a housing and a reflective element includedwithin said housing; a video device, said video device including animaging sensor, said imaging sensor being positioned at said interiorrearview mirror assembly and having a field of view forward and throughthe windshield, said imaging sensor being operable to at least senseprecipitation at at least one of an exterior surface of the windshieldand an interior surface of the windshield; a control operable to receivea signal from said imaging sensor, said control being operable tocontrol a headlamp of the vehicle and to control at least one of awindshield wiper of the vehicle and a defogging system of the vehicle inresponse to said signal; and an illumination device for illuminating thefield of view of said imaging sensor, said illumination device being atleast occasionally activated, wherein said imaging sensor is operable tosense a level of ambient light present at the windshield, saidillumination device being activated in response to said imaging sensorsensing low light conditions.
 45. The interior rearview mirror system ofclaim 44, wherein said control is operable to control a headlamp of thevehicle in response to said imaging sensor sensing low light conditions.46. An interior rearview mirror system suitable for use in a vehicle,said interior rearview mirror system comprising: an interior rearviewmirror assembly adapted for attachment to an interior portion of thevehicle, said interior rearview mirror assembly comprising a housing anda reflective element included within said housing; and a video device,said video device including an imagine sensor, said imaging sensor beingpositioned at said interior rearview mirror assembly and having a fieldof view forward and through the windshield, said imaging sensor beingoperable to at least sense precipitation at at least one of an exteriorsurface of the windshield and an interior surface of the windshieldwherein said video device includes a polarizing filter; and a controloperable to receive a signal from said imaging sensor, said controlbeing operable to control a headlamp of the vehicle and to control atleast one of a windshield wiper of the vehicle and a defogging system ofthe vehicle in response to said signal.
 47. The interior rearview mirrorsystem of claim 46, wherein said polarizing filter is at leastoccasionally positionable between said imaging sensor and thewindshield, said polarizing filter being operable to attenuate polarizedlight from the windshield.
 48. An interior rearview mirror systemsuitable for use in a vehicle, said interior rearview mirror systemcomprising: an interior rearview mirror assembly adapted for attachmentto an interior portion of the vehicle, said interior rearview mirrorassembly comprising a housing and a reflective element included withinsaid housing; and a video device, said video device including an imagingsensor, said imaging sensor having a field of view forward through thewindshield, said imaging sensor being operable to at least senseprecipitation at at least one of an exterior surface of the windshieldand an interior surface of the windshield; and a control operable toreceive a signal from said imaging sensor, said control being operableto digitally process said signal and to control at least two of(i) aheadlamp of the vehicle, (ii) a windshield wiper of the vehicle, (iii) adefogging system of the vehicle and (iv) a movable window of the vehiclein response to said signal, wherein said imaging sensor is operable as acomponent of an active cruise control system.
 49. The interior rearviewmirror system of claim 48, wherein said imaging sensor is operable todetermine the speed at which the vehicle is traveling.
 50. An interiorrearview mirror suitable for use in a vehicle, said interior rearviewmirror system comprising: an interior rearview mirror assembly adaptedfor attachment to an interior portion of the vehicle, said interiorrearview mirror assembly comprising a housing and a reflective elementincluded within said housing; and a video device, said video deviceincluding an imaging sensor, said imaging sensor having a field of viewforward through the windshield, said imaging sensor being operable to atleast sense precipitation at at least one of an exterior surface of thewindshield and an interior surface of the windshield, said imagingsensor being operable to sense water droplets at the exterior surface ofthe windshield and fog particles at the interior surface of thewindshield; and a control operable to receive a signal from said imagingsensor, said control being operable to digitally process said signal andto control at least two of(i) a headlamp of the vehicle, (ii) awindshield wiper of the vehicle, (iii) a defogging system of the vehicleand (iv) a movable window of the vehicle in response to said signal,said control being operable to control a windshield wiper of the vehiclein response to the presence of water droplets at the exterior surface ofthe windshield and to control a defogging system of the vehicle inresponse to the presence of for particles at the interior surface of thewindshield wherein said control is operable to control a headlamp of thevehicle in response to the presence of water droplets at the exteriorsurface of the windshield.
 51. The interior rearview minor system ofclaim 50, wherein said control is operable to control a headlamp of thevehicle in response to a level of light present at the windshield. 52.The interior rearview mirror system of claim 50, wherein said control isoperable to control a movable window of the vehicle in response to thepresence of water droplets at the exterior surface of the windshield.53. An interior rearview mirror system suitable for use in a vehicle,said interior rearview mirror system comprising: an interior rearviewmirror assembly adapted for attachment to an interior portion of thevehicle, said interior rearview mirror assembly comprising a housing anda reflective element included within said housing; and a video device,said video device including an imaging sensor, said imagine sensorhaving a field of view forward through the windshield, said imagingsensor being operable to at least sense precipitation at at least one ofan exterior surface of the windshield and an interior surface of thewindshield, said imaging sensor being operable to sense water dropletsat the exterior surface of the windshield and fog particles at theinterior surface of the windshield; and a control operable to receive asignal from said imaging sensor, said control being operable todigitally process said signal and to control at least two of (i) aheadlamp of the vehicle, (ii) a windshield wiper of the vehicle, (iii) adefogging system of the vehicle and (iv) a movable window of the vehiclein response to said signal, said control being operable to control awindshield wiper of the vehicle in response to the presence of waterdroplets at the exterior surface of the windshield and to control adefogging system of the vehicle in response to the presence of fogparticles at the interior surface of the windshield, said control beingoperable to vary a rate of wipe of a windshield wiper of the vehicle,wherein said control is operable to vary the rate of wipe according to adensity of water droplets on the exterior surface of the windshield. 54.The interior rearview mirror system of claim 53, wherein said control isoperable to control a headlamp of the vehicle and to control awindshield wiper of the vehicle in response to said signal.
 55. Theinterior rearview mirror system of claim 53, wherein said control isoperable to control a movable window of the vehicle in response to saidsignal, said movable window comprising a sunroof of the vehicle.
 56. Theinterior rearview mirror system of claim 55, wherein said control isoperable to control the sunroof of the vehicle to close the sunroof inresponse to the presence of precipitation at the exterior surface of thewindshield.
 57. The interior rearview mirror system of claim 48, whereinsaid control comprises a micro-computer having at least one of anembedded control application, a custom digital logic circuit and adigital signal processor circuit.
 58. The interior rearview mirrorsystem of claim 57, wherein said imaging array comprises circuitrycapable of producing at least one digital signal.
 59. The interiorrearview mirror system of claim 53, wherein said control is operable tocontrol a headlamp of the vehicle in response to a level of light sensedat the vehicle.
 60. The interior rearview mirror system of claim 59,wherein said imaging sensor is operable to sense a level of ambientlight present at the vehicle.
 61. The interior rearview mirror system ofclaim 60, wherein said control is operable to control a headlamp of thevehicle in response to said imaging sensor sensing low light conditions.62. The interior rearview mirror system of claim 53, wherein saidinterior rearview mirror assembly comprises an electrochromic interiorrearview mirror assembly and said reflective element comprises anelectrochromic reflective element, said electrochromic interior rearviewmirror assembly comprising electrochromic control circuitry forcontrolling said electrochromic reflective element.
 63. The interiorrearview mirror system of claim 62, wherein said control shares at leastone component of said electrochromic control circuitry.
 64. The interiorrearview mirror system of claim 63, wherein said control shares said atleast one component on a common circuit board of said electrochromicinterior rearview mirror assembly.
 65. The interior rearview mirrorsystem of claim 53, wherein said control is operable to control at leastone other accessory of the vehicle.
 66. The interior rearview mirrorsystem of claim 53 including an illumination device for illuminating thefield of view of said imaging sensor.
 67. The interior rearview mirrorsystem of claim 66, wherein said illumination provides infraredillumination.
 68. The interior rearview mirror system of claim 66,wherein said illumination device is at least occasionally activated. 69.The interior rearview mirror system of claim 68, wherein saidillumination device is pulsed on and off.
 70. The interior rearviewmirror system of claim 53, wherein said imaging sensor comprises animaging array sensor.
 71. The interior rearview mirror system of claim70, wherein said imaging array sensor comprises a pixelated imagingarray sensor.
 72. The interior rearview mirror system of claim 70,wherein said imaging array sensor comprises a CMOS sensor.
 73. Theinterior rearview mirror system of claim 53, wherein said video deviceincludes a lens disposed between said imaging sensor and an interiorsurface of the windshield of the vehicle.
 74. The interior rearviewmirror system of claim 73, wherein said lens functions establish a smalldepth of field.
 75. The interior rearview mirror system of claim 74,wherein said lens focuses said imaging sensor on an area at orimmediately adjacent to the windshield of the vehicle.
 76. An interiorrearview mirror system suitable for use in a vehicle, said interiorrearview mirror system comprising: an interior rearview mirror assemblyadapted for attachment to an interior portion of the vehicle, saidinterior rearview mirror assembly comprising a housing and a reflectiveelement included within said housing; and a video device, said videodevice including an imaging sensor, said imaging sensor having a fieldof view forward through the windshield, said imaging a sensor beingoperable to at least sense precipitation at at least one of an exteriorsurface of the windshield and an interior surface of the windshield; anda control operable to receive a signal from said imaging sensor, saidcontrol being operable to digitally Process said signal and to controlat least two of(i) a headlamp of the vehicle, (ii) a windshield wiper ofthe vehicle, (iii) a defogging system of the vehicle and (iv) a movablewindow of the vehicle in response to said signal, said imaging sensorbeing operable to sense foe particles at the interior surface of thewindshield, said control being operable to control a defogging system ofthe vehicle in response to said imagine sensor sensing foe particles atthe interior surface of the windshield wherein said control is operableto adjust a blower level of the defogging system of the vehicle inresponse to a density of the fog particles sensed at the interiorsurface of the windshield.
 77. An interior rearview mirror systemsuitable for use in a vehicle, said interior rearview mirror systemcomprising: an interior rearview mirror assembly adapted for attachmentto an interior portion of the vehicle, said interior rearview mirrorassembly comprising a housing and a reflective element included withinsaid housing; and a video device, said video device including an imaginesensor, said imaging sensor having a field of view forward through thewindshield, said imaging sensor being operable to at least senseprecipitation at at least one of an exterior surface of the windshieldand an interior surface of the windshield, said imagine sensor beingoperable to sense water droplets at an exterior surface of thewindshield; and a control operable to receive a signal from said imaginesensor, said control being operable to digitally process said signal andto control at least two of (i) a headlamp of the vehicle, (ii) awindshield wiper of the vehicle, (iii) a defogging system of the vehicleand (iv) a movable window of the vehicle in response to said signal,said control being operable to control a windshield wiper of the vehiclein response to said imaging sensor sensing water droplets at theexterior surface of the windshield, said control being operable toadjust a rate of wipe of a windshield wiper of the vehicle, said controlbeing operable to control a rear window wiper of the vehicle, saidcontrol being operable to control a rear window wiper in response tosaid imaging sensor sensing water droplets at the exterior surface ofthe windshield, wherein said control causes a rear window wiper to cyclefor every N cycles of a windshield wiper, wherein N is greater than one.78. The interior rearview mirror system of claim 77, wherein the valueof N varies as a function of the speed of a windshield wiper.
 79. Aninterior rearview mirror system suitable for use in a vehicle, saidinterior rearview mirror system comprising: an interior rearview mirrorassembly adapted for attachment to an interior portion of the vehicle,said interior rearview mirror assembly comprising a housing and areflective element included within said housing; and a video device,said video device including an imaging sensor, said imaging sensorhaving a field of view forward through the windshield, said imagingsensor being operable to at least sense precipitation at at least one ofan exterior surface of the windshield and an interior surface of thewindshield; and a control operable to receive a signal from said imagingsensor, said control being operable to digitally process said signal andto control at least two of(i) a headlamp of the vehicle, (ii) awindshield wiper of the vehicle, (iii) a defogging system of the vehicleand (iv) a movable window of the vehicle in response to said signal; andan illumination device for illuminating the field of view of saidimaging sensor, said illumination device being pulsed on and off,wherein said imaging sensor comprises a shutter for exposing saidimaging sensor to the field of view forwardly and through thewindshield.
 80. The interior rearview mirror system of claim 79, whereinduring low light conditions, said shutter is opened to expose saidimaging sensor to the windshield when said illumination device is pulsedon and closed to not expose said imaging sensor to the windshield whensaid illumination device is pulsed off.
 81. An interior rearview mirrorsystem suitable for use in a vehicle, said interior rearview mirrorsystem comprising: an interior rearview mirror assembly adapted forattachment to an interior portion of the vehicle, said interior rearviewmirror assembly comprising a housing and a reflective element includedwithin said housing; and a video device, said video device including animaging sensor, said imaging sensor having a field of view forwardthrough the windshield, said imaging sensor being operable to at leastsense precipitation at at least one of an exterior surface of thewindshield and an interior surface of the windshield; and a controloperable to receive a signal from said imaging sensor, said controlbeing operable to digitally process said signal and to control at leasttwo of(i) a headlamp of the vehicle, (ii) a windshield wiper of thevehicle, (iii) a defogging system of the vehicle and (iv) a movablewindow of the vehicle in response to said signal; and an illuminationdevice for illuminating the field of view of said imaging sensor, saidillumination device being at least occasionally activated, wherein saidillumination device is activated during low light conditions.
 82. Theinterior rearview mirror system of claim 57, wherein said imaging sensoris operable to sense water droplets at the exterior surface of thewindshield and fog particles at the interior surface of the windshield.83. The interior rearview mirror system of claim 82, wherein saidcontrol is operable to control a windshield wiper of the vehicle inresponse to the presence of water droplets at the exterior surface ofthe windshield and to control a defogging system of the vehicle inresponse to the presence of fog particles at the interior surface of thewindshield.
 84. The interior rearview mirror system of claim 83, whereinsaid control is operable to vary a rate of wipe of a windshield wiper ofthe vehicle.
 85. The interior rearview mirror system of claim 81,wherein said imaging sensor is operable to sense fog particles at theinterior surface of the windshield, said control being operable tocontrol a defogging system of the vehicle in response to said imagingsensor sensing fog particles at the interior surface of the windshield.86. The interior rearview mirror system of claim 81, wherein saidimaging sensor is operable to sense water droplets at an exteriorsurface of the windshield, said control being operable to control awindshield wiper of the vehicle in response to said imaging sensorsensing water droplets at the exterior surface of the windshield. 87.The interior rearview mirror system of claim 81, wherein said control isoperable to adjust a rate of wipe of a windshield wiper of the vehicle.88. The interior rearview mirror system of claim 87, wherein saidcontrol is operable to adjust the rate of wipe in response to a quantityof the water droplets sensed at the exterior surface of the windshield.89. The interior rearview mirror system of claim 87, wherein saidcontrol is operable to control a rear window wiper of the vehicle. 90.The interior rearview minor system of claim 89, wherein said control isoperable to control a rear window wiper in response to said imagingsensor sensing water droplets at the exterior surface of the windshield.91. An interior rearview mirror system suitable for use in a vehicle,said interior rearview mirror system comprising: an interior rearviewmirror assembly adapted for attachment to an interior portion of thevehicle, said interior rearview mirror assembly comprising a housing anda reflective element included within said housing; and a video device,said video device including an imaging sensor, said imaging sensorhaving a field of view forward through the windshield, said imagingsensor being operable to at least sense precipitation at at least one ofan exterior surface of the windshield and an interior surface of thewindshield; and a control operable to receive a signal from said imagingsensor, said control being operable to digitally process said signal andto control at least two of(i) a headlamp of the vehicle, (ii) awindshield wiper of the vehicle, (iii) a defogging system of the vehicleand (iv) a movable window of the vehicle in response to said signal; andan illumination device for illuminating the field of view of saidimaging sensor, said illumination device being at least occasionallyactivated wherein said imaging sensor is operable to sense a level ofambient tight present at the windshield, said illumination device beingactivated in response to said imaging sensor sensing low lightconditions.
 92. The interior rearview mirror system of claim 91, whereinsaid control is operable to control a headlamp of the vehicle inresponse to said imaging sensor sensing low light conditions.
 93. Aninterior rearview mirror system suitable for use in a vehicle, saidinterior rearview mirror system comprising: an interior rearview mirrorassembly adapted for attachment to an interior portion of the vehicle,said interior rearview mirror assembly comprising a housing and areflective element included within said housing; and a video device,said video device including an imagine sensor, said imaging sensorhaving a field of view forward through the windshield, said imagingsensor being operable to at least sense precipitation at at least one ofan exterior surface of the windshield and an interior surface of thewindshield wherein said video device includes a polarizing filter; and acontrol operable to receive a signal from said imaging sensor, saidcontrol being operable to digitally process said signal and to controlat least two of (i) a headlamp of the vehicle, (ii) a windshield wiperof the vehicle, (iii) a defogging system of the vehicle and (iv) amovable window of the vehicle in response to said signal.
 94. Theinterior rearview mirror system of claim 93, wherein said polarizingfilter is at least occasionally positionable between said imaging sensorand the windshield, said polarizing filter being operable to attenuatepolarized light from the windshield.
 95. An interior rearview mirrorsystem suitable for use in a vehicle, said interior rearview mirrorsystem comprising; an electrochromic interior rearview mirror assemblyadapted for attachment to an interior portion of the vehicle, saidinterior rearview mirror assembly comprising a housing and anelectrochromic reflective element included within said housing saidelectrochromic interior rearview mirror assembly comprisingelectrochromic control circuitry for controlling said electrochromicreflective element; and a video device, said video device including animagine array sensor, said imaging array sensor having a field of viewforward through the windshield; and a control sharing at least onecomponent of said electrochromic control circuitry, said controlreceiving a signal from said imaging array sensor and being operable todigitally process said signal and to control at least two of (i) aheadlamp of the vehicle, (ii) a windshield wiper of the vehicle, (iii) adefogging system of the vehicle and (iv) a movable window of the vehiclein response to said signal, wherein said imaging array sensor isoperable as a component of an active cruise control system.
 96. Theinterior rearview mirror system of claim 95, wherein said imaging arraysensor is operable to determine the speed at which the vehicle istraveling.
 97. An interior rearview mirror system suitable for use in avehicle, said interior rearview mirror system comprising: anelectrochromic interior rearview mirror assembly adapted for attachmentto an interior portion of the vehicle, said interior rearview mirrorassembly comprising a housing and an electrochromic reflective elementincluded within said housing, said electrochromic interior rearviewmirror assembly comprising electrochromic control circuitry (orcontrolling said electrochromic reflective element; and a video device,said video device including an imaging a array sensor, said imagingarray sensor having a field of view forward through the windshield, saidimaging array sensor being operable to sense precipitation at at leastone of an exterior surface of the windshield and an interior surface ofthe windshield, said imaging array sensor being operable to sense waterdroplets at the exterior surface of the windshield and fog particles atthe interior surface of the windshield; and a control sharing at leastone component of said electrochromic control circuitry, said controlreceiving a signal from said imaging array sensor and being operable todigitally process said signal and to control at least two of(i) aheadlamp of the vehicle, (ii) a windshield wiper of the vehicle, (ii) adefogging system of the vehicle and (iv) a movable window of the vehiclein response to said signal, said control being operable to control awindshield wiper of the vehicle in response to the presence of waterdroplets at the exterior surface of the windshield and to control adefogging system of the vehicle in response to the presence of fogparticles at the interior surface of the windshield, wherein saidcontrol is operable to control a headlamp of the vehicle in response tothe presence of water droplets at the exterior surface of thewindshield.
 98. The interior rearview mirror system of claim 97, whereinsaid control is operable to control a headlamp of the vehicle inresponse to a level of light present at the windshield.
 99. The interiorrearview mirror system of claim 97, wherein said imaging array sensor isoperable to sense a level of ambient light present at the vehicle. 100.The interior rearview mirror system of claim 99, wherein said control isoperable to control the headlamp of the vehicle in response to saidimaging array sensor sensing low light conditions.
 101. The interiorrearview mirror system of claim 97, wherein said control is operable tocontrol a movable window of the vehicle in response to the presence ofwater droplets at the exterior surface of the windshield.
 102. Aninterior rearview mirror system suitable for use in a vehicle, saidinterior rearview mirror system comprising: an electrochromic interiorrearview mirror assembly adapted for attachment to an interior portionof the vehicle, said interior rearview mirror assembly comprising ahousing and an electrochromic reflective element included within saidhousing, said electrochromic interior rearview mirror assemblycomprising electrochromic control circuitry for controlling saidelectrochromic reflective element; and a video device, said video deviceincluding an imaging array sensor, said imaging array sensor having afield of view forward through the windshield, said imaging array sensorbeing operable to sense precipitation at at least one of an exteriorsurface of the windshield and an interior surface of the windshield,said imaging array sensor being operable to sense water droplets at theexterior surface of the windshield and fog particles at the interiorsurface of the windshield; and a control sharing at least one componentof said electrochromic control circuitry, said control receiving asignal from said imaging array sensor and being operable to digitallyprocess said signal and to control at least two of (i) headlamp of thevehicle, (ii) a windshield wiper of the vehicle, (iii) a defoggingsystem of the vehicle and (iv) a movable window of the vehicle inresponse to said signal, said control being operable to control awindshield wiper of the vehicle in response to the presence of waterdroplets at the exterior surface of the windshield and to control adefogging system of the vehicle in response to the presence of fogparticles at the interior surface of the windshield, said control beingoperable to vary a rate of wipe of a windshield wiper of the vehicle,wherein said control is operable to vary the rate of wipe according to adensity of water droplets present at the exterior surface of thewindshield.
 103. The interior rearview mirror system of claim 102,wherein said control shares said at least one component on a commoncircuit board of said electrochromic interior rearview mirror assembly.104. The interior rearview mirror system of claim 102, wherein saidcontrol is operable to control a headlamp of the vehicle and to controla windshield wiper of the vehicle in response to said signal.
 105. Theinterior rearview mirror system of claim 102, wherein said control isoperable to control a movable window of the vehicle in response to saidsignal, said movable window comprising a sunroof of the vehicle. 106.The interior rearview mirror system of claim 105, wherein said controlis operable to control the sunroof of the vehicle to close the sunroofin response to the presence of precipitation at an exterior surface ofthe vehicle.
 107. The interior rearview mirror system of claim 102,wherein said control comprises a micro-computer having at least one ofan embedded control application, a custom digital logic circuit and adigital signal processor circuit.
 108. The interior rearview mirrorsystem of claim 102, wherein said control is operable to control aheadlamp of the vehicle in response to a level of light sensed at thevehicle.
 109. The interior rearview mirror system of claim 108, whereinsaid imaging array sensor is operable to sense a level of ambient lightpresent at the vehicle.
 110. The interior rearview mirror system ofclaim 109, wherein said control is operable to control a headlamp of thevehicle in response to said imaging array sensor sensing low lightconditions.
 111. The interior rearview mirror system of claim 102,wherein said control is operable to control at least one other accessoryof the vehicle.
 112. The interior rearview mirror system of claim 102including an illumination device for illuminating the field of view ofsaid imaging array sensor.
 113. The interior rearview mirror system ofclaim 112, wherein said illumination device provides infraredillumination.
 114. The interior rearview mirror system of claim 112,wherein said illumination device is at least occasionally activated.115. The interior rearview mirror system of claim 114, wherein saidillumination device is pulsed on and off.
 116. The interior rearviewmirror system of claim 102, wherein said imaging array sensor comprisesa pixelated imaging array sensor.
 117. The interior rearview mirrorsystem of claim 102, wherein said imaging array sensor comprises a CMOSsensor.
 118. The interior rearview mirror system of claim 102, whereinsaid video device includes a lens disposed between said imaging arraysensor and the interior surface of the windshield of the vehicle. 119.The interior rearview mirror system of claim 102, wherein said lensfunctions establish a small depth of field.
 120. The interior rearviewmirror system of claim 119, wherein said lens focuses said imaging arraysensor on an area at or immediately adjacent to the windshield of thevehicle.
 121. An interior rearview mirror system suitable for use in avehicle, said interior rearview mirror system comprising: anelectrochromic interior rearview mirror assembly adapted for attachmentto an interior portion of the vehicle, said interior rearview mirrorassembly comprising a housing and an electrochromic reflective elementincluded within said housing, said electrochromic interior rearviewmirror assembly comprising electrochromic control circuitry forcontrolling said electrochromic reflective element; and a video device,said video device including an imagine array sensor, said imaging arraysensor having a field of view forward through the windshield, saidimaging array sensor being operable to sense fog particles at aninterior surface of the windshield; and a control sharing at least onecomponent of said electrochromic control circuitry, said controlreceiving a signal from said imaging array sensor and being operable todigitally process said signal and to control at least two of (i) aheadlamp of the vehicle, (ii) a windshield wiper of the vehicle, (iii) adefogging system of the vehicle and (iv) a movable window of the vehiclein response to said signal, said control being operable to control adefogging system of the vehicle in response to said imaging array sensorsensing fog particles at the interior surface of the windshield, whereinsaid control is operable to adjust a blower level of the defoggingsystem of the vehicle in response to a density of the fog particlessensed at the interior surface of the windshield.
 122. An interiorrearview mirror system suitable for use in a vehicle, said interiorrearview mirror system comprising: an electrochromic interior rearviewmirror assembly adapted for attachment to an interior portion of thevehicle, said interior rearview mirror assembly comprising a housing andan electrochromic reflective element included within said housing saidelectrochromic interior rearview mirror assembly comprisingelectrochromic control circuitry for controlling said electrochromicreflective element; and a video device, said video device including animaging array sensor, said imaging array sensor having a field of viewforward through the windshield, said imaging a array sensor beingoperable to sense water droplets at an exterior surface of thewindshield; and a control sharing at least one component of saidelectrochromic control circuitry, said control receiving a signal fromsaid imagine array sensor and being operable to digitally process saidsignal and to control at least two of(i) a headlamp of the vehicle, (ii)a windshield wiper of the vehicle, (iii) a defogging system of thevehicle and (iv) a movable window of the vehicle in response to saidsignal, said control being operable to control a windshield wiper of thevehicle in response to said imaging array sensor sensing water dropletsat the exterior surface of the windshield, said control being operableto adjust a rate of wine of a windshield wiper of the vehicle, saidcontrol being operable to control a rear window wiper of the vehicle inresponse to said imaging array sensor sensing water droplets at theexterior surface of the windshield wherein said control causes a rearwindow wiper to cycle for every N cycles of a windshield wiper, whereinN is greater than one.
 123. The interior rearview mirror system of claim122, wherein the value of N varies as a function of the speed of awindshield wiper.
 124. An interior rearview mirror system suitable foruse in a vehicle, said interior rearview mirror system comprising: anelectrochromic interior rearview mirror assembly adapted for attachmentto an interior portion of the vehicle, said interior rearview mirrorassembly comprising a housing and an electrochromic reflective elementincluded within said housing, said electrochromic interior rearviewmirror assembly comprising electrochromic control circuitry forcontrolling said electrochromic reflective element; and a video device,said video device including an imagine array sensor, said imagine arraysensor having a field of view forward through the windshield; and acontrol sharing at least one component of said electrochromic controlcircuitry, said control receiving a signal from said imaging arraysensor and being operable to digitally process said signal and tocontrol at least two of (i) a headlamp of the vehicle, (ii) a windshieldwiper of the vehicle, (iii) a defogging system of the vehicle and (iv) amovable window of the vehicle in response to said signal; and anillumination device for illuminating the field of view of said imagingarray sensor, said illumination device being pulsed on and off whereinsaid imaging array sensor comprises a shutter for exposing said imagingarray sensor to the field of view forwardly and through the windshield.125. The interior rearview mirror system of claim 124, wherein duringtow light conditions, said shutter is opened to expose said imagingarray sensor to the windshield when said illumination device is pulsedon and closed to not expose said imaging army sensor to the windshieldwhen said illumination device is pulsed off.
 126. An interior rearviewmirror system suitable for use in a vehicle, said interior rearviewmirror system comprising: an electrochromic interior rearview mirrorassembly adapted for attachment to an interior portion of the vehicle,said interior rearview mirror assembly comprising a housing and anelectrochromic reflective element included within said housing, saidelectrochromic interior rearview mirror assembly comprisingelectrochromic control circuitry for controlling said electrochromicreflective element; and a video device, said video device including animaging array sensor, said imaging array sensor having a field of viewforward through the windshield; and a control sharing at least onecomponent of said electrochromic control circuitry, said controlreceiving a signal from said imaging array sensor and being operable todigitally process said signal and to control at least two of(i) aheadlamp of the vehicle, (ii) a windshield wiper of the vehicle, (iii) adefogging system of the vehicle and (iv) a movable window of the vehiclein response to said signal; and an illumination device for illuminatingthe field of view of said imaging array sensor, said illumination devicebeing at least occasionally activated, wherein said illumination deviceis activated during low light conditions.
 127. The interior rearviewmirror system of claim 126, wherein said imaging array sensor isoperable to sense precipitation at at least one of an exterior surfaceof the windshield and an interior surface of the windshield.
 128. Theinterior rearview mirror system of claim 127, wherein said imaging arraysensor is operable to sense water droplets at the exterior surface ofthe windshield and fog particles at the interior surface of thewindshield.
 129. The interior rearview mirror system of claim 128,wherein said control is operable to control a windshield wiper of thevehicle in response to the presence of water droplets at the exteriorsurface of the windshield and to control a defogging system of thevehicle in response to the presence of fog particles at the interiorsurface of the windshield.
 130. The interior rearview minor system ofclaim 129, wherein said control is operable to vary a rate of wipe of awindshield wiper of the vehicle.
 131. The interior rearview mirrorsystem of claim 126, wherein said imaging array sensor is operable tosense fog particles at an interior surface of the windshield, saidcontrol being operable to control a defogging system of the vehicle inresponse to said imaging array sensor sensing fog particles at theinterior surface of the windshield.
 132. The interior rearview mirrorsystem of claim 126, wherein said imaging array sensor is operable tosense water droplets at an exterior surface of the windshield, saidcontrol being operable to control a windshield wiper of the vehicle inresponse to said imaging array sensor sensing water droplets at theexterior surface of the windshield.
 133. The interior rearview mirrorsystem of claim 132, wherein said control is operable to adjust a rateof wipe of a windshield wiper of the vehicle.
 134. The interior rearviewmirror system of claim 133, wherein said control is operable to adjustthe rate of wipe in response to a quantity of the water droplets sensedat the exterior surface of the windshield.
 135. The interior rearviewmirror system of claim 133, wherein said control is operable to controla rear window wiper of the vehicle.
 136. The interior rearview mirrorsystem of claim 135, wherein said control is operable to control a rearwindow wiper in response to said imaging array sensor sensing waterdroplets at the exterior surface of the windshield.
 137. An interiorrearview mirror system suitable for use in a vehicle, said interiorrearview mirror system comprising: an electrochromic interior rearviewmirror assembly adapted for attachment to an interior portion of thevehicle, said interior rearview mirror assembly comprising a housing andan electrochromic reflective element included within said housing, saidelectrochromic interior rearview mirror assembly comprisingelectrochromic control circuitry for controlling said electrochromicreflective element; and a video device, said video device including animaging array sensor, said imaging array sensor having a field of viewforward through the windshield; and a control sharing at least onecomponent of said electrochromic control circuitry, said controlreceiving a signal from said imaging array sensor and being operable todigitally process said signal and to control at least two of(i) aheadlamp, of the vehicle, (ii) a windshield wiper of the vehicle, (iii)a defogging system of the vehicle and (iv) a movable window of thevehicle in response to said signal; and an illumination device forilluminating the field of view of said imaging array sensor, saidillumination device being at least occasionally activated, wherein saidimaging array sensor is operable to sense a level of ambient lightpresent at the windshield, said illumination device being activated inresponse to said imaging array sensor sensing low light conditions. 138.The interior rearview mirror system of claim 137, wherein said controlis operable to control a headlamp of the vehicle in response to saidimaging array sensor sensing low light conditions.
 139. An interiorrearview mirror system suitable for use in a vehicle, said interiorrearview mirror system comprising: an electrochromic interior rearviewmirror assembly adapted for attachment to an interior portion of thevehicle, said interior rearview mirror assembly comprising a housing andan electrochromic reflective element included within said housing, saidelectrochromic interior rearview mirror assembly comprisingelectrochromic control circuitry for controlling said electrochromicreflective element; and a video device, said video device including animaging array sensor, said imagine array sensor having a field of viewforward through the windshield, wherein said video device includes apolarizing filter; and a control sharing at least one component of saidelectrochromic control circuitry, said control receiving a signal fromsaid imaging array sensor and being operable to digitally process saidsignal and to control at least two of (i) a headlamp of the vehicle,(ii) a windshield wiper of the vehicle, (iii) a defogging system of thevehicle and (iv) a movable window of the vehicle in response to saidsignal.
 140. The interior rearview mirror system of claim 139, whereinsaid polarizing filter is at least occasionally positionable betweensaid imaging array sensor and the windshield, said polarizing filterbeing operable to attenuate polarized light from the windshield.